


THE MANUFACTURERS 

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WISH TO HELP YOU 


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A ctiL. /C* 

RICHARDSON’S 

HANDBOOK 

OF 

PROJECTION 

FOR THEATRE MANAGERS AND 
MOTION PICTURE PROJECTIONISTS 


FOURTH EDITION 


PUBLISHED BY 

CHALMERS PUBLISHING COMPANY 

516 FIFTH AVENUE 
NEW YORK CITY 








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Copyright in United States, 1922; 
Copyright in Great Britain, 1922; 
Copyright in Canada, 1922, 

by 

Chalmers Publishing Company 

New York. 


All Rights Reserved. 



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Author’s Note 

I HAVE striven hard to make this, the fourth edition of my 
handbook of projection, worthy of the sincere commendation 
of those who will consult its pages. It is not perfect—true, 
but few things in this world are perfect, and I have faith to be¬ 
lieve those who use the book will look with kindly eyes upon 
its shortcomings, remembering that the work was a large one, and 
that much of the ground had to be broken as virgin sod. 

I want to embrace this opportunity to tender my sincere 
thanks to those thousands of users of former editions of the 
handbook who have said such kindly things concerning them. 
Their words of commendation have given me courage to com¬ 
plete the compilation of this, the fourth edition, at times when 
the burden of the work seemed unbearably heavy. 






Publisher’s Word 

I N October, 1910, this company brought out the first edition 
of the Handbook of Projection, by F. H. Richardson. 
Since that time three separate editions, each bigger and 
better than the other, have been published and sold. It is 
with pardonable pride that we now offer to the motion pic¬ 
ture industry this new edition which is the largest, most com¬ 
plete, and accurate treatise on projection ever written. We 
firmly believe the motion picture industry will find that this, 
the fourth edition, far surpasses its predecessors in scope 
and arrangement of contents. In the constant endeavor for 
finer and healthier entertainment on the screen, projection 
has played a most important role. We therefore offer this 
latest work by Mr. Richardson in the field of projection with 
the sincere belief that all who read it will be helped and a 
great industry thereby benefited. 

CHALMERS PUBLISHING COMPANY. 


MANAGERS AND PROJECTIONISTS 


Index 

T O make a really satisfactory index for a work of this 
kind presents a most difficult problem. I have found a 
strictly alphabetical index to be far from satisfying, and 
have therefore adopted a new plan in this edition, which, I 
hope and believe, will serve very well. If you want something 
concerning the screen, look under the heading of “Screen.” 
If it is something about a projector, look under projectors, 
and so on. The plan is not perfect, but, I believe, it is 
much better than a straight alphabetical arrangement. 

THE AUTHOR. 


Ammeter and Voltmeter 

Should Be One of Each in the Projection Room.... 334 


How to Connect. 335 

Arc, The 

Also see Light Source, The, and Carbons 

Figuring Resistance of. 57 

Voltage Constants. 56 

A. C. Voltage Drop. 58 

Crater Temperature. 392 

Crater Not of Even Luminosity. 172 

Intrinsic Brilliancy of Crater.378 and 392 

Rule o’ Thumb. 59 

Relative Brilliancy, High Intensity and Ordinary.... 869 

Gas Stream Between Carbon Tips.375 and 376 

Resistance of Various Elements of Arc.391 

What Produces Light in Electric Arc. 391 

Arc Controllers 

General Remarks. 372 

Automatic and Mechanical Arc Controls.559 to 586 

Principle on Which Automatic Controls Operate, 

559 and 560 

How the Mechanical Arc Feed Works. 560 

Why Controllers Should Be Used. 560 

Fulco Speedco Automatic Arc Control.562 to 569 

Hallberg Continuous Feed Arc Control.570 to 574 


iii 



















HANDBOOK OF PROJECTION FOR 


Peerless Automatic Arc Control.574 to 577 

Tepeco Mechanical Arc Feed.578 to 580 

Simplex Mechanical Arc Control.580 to 585 

Motiograph Mechanical Arc Control.585 to 586 

Arc, High Intensity 

High Intensity Arc, General Remarks. 773 

General Electric High Intensity Arc Lamp....774 to 782 

Sunlight High Intensity Arc Lamp.783 to 793 

Simplex High Intensity Arc Lamp. 585 

Batteries 

Wet Battery—What It Consists of.6 and 7 

Copper Pole of Battery Positive. 7 

Voltage of Battery. 7 

Batteries Are for Light Work. 7 

Different Dry Battery Connections. 897 

Carbons 

Also see Light Source and Arc 

How They Are Made. 374 

What the Core Is for and What It Does. 374 

Solid vs. Cored Negative Carbons. 377 

Carbon Size. 377 

Relation of Amperage to Crater Size.381, 393-394 

Relation of Amperage to Candle Power.379 and 392 

Candle Power per Ampere and Carbon Size, Current 

Remaining Stationary. 379 

Rule by Which We Must Be Guided. 384 

Projectionist Should Inspect Carbons. 387 

Hard and Soft Carbons. 387 

Care of Carbons. 388 

Alternating Current Carbons... 389 

Crater Area and Dimensions per Ampere. 393 

Setting the Carbons. 402 

Condenser 

What the Condenser Does.126-172 

Types of Condenser and Description Thereof. 168 

Effect of Distance of Light Source from Collector 

Lens. 162 

“Collector” and “Converging” Lens—What They 

Are .24 and 25 

Effect of Placing Flat Sides of Plano Convex Lenses 
Together. 168 

iv 

































MANAGERS AND PROJECTIONISTS 

Serious Objection to Large Diameter Condenser, 

170, 203 and 205 


Proper Spacing of Condenser Lenses. 170 

Reason for 1/16-Inch Spacing of Lenses.170-171 

Discolored Lenses, Practical Effect of. 164 

Discolored Lenses—What to Do with Them. 165 

Pitted Collector Lens, Effect of. 165 

Lens Edge Thickness, Importance of. 166 

Polish and True Curvature, Importance of. 167 

Meniscus Bi-Convex, When to Use.... 169 

•Small Diameter Condensers. 169 

Condenser Mounts . 171 

Light Loss Between Lenses. 171 

Condenser Breakage . 171 

Magnification of Light Source at Spot. 175 

Ghost Zone in Condenser Beam. 177 

Effect of Condenser Distance from Aperture on 

Divergence of Beam Beyond Aperture. 184 

Universal Method of Selecting Condenser and Ascer¬ 
taining Its Proper Distance from Aperture... 194-202 

Condenser Diameter. 203 

Requirements of Good Condenser Holder. 367 

Advantage of Locating Condenser Inside Lamp 

House. 368 

Inside Dowser. 368 


Crater Angle 

See The Light Source 

Current 

Also see Electrical Action 

Alternating and Direct. 13 

Why A. C. Is More Generally Used Than D. C.13-14 

Relation of Volts and Amperes to Power. 13 

Action of A. C. 16 

Objection to Low Frequency Current. 15 

Single, Two and Three-Phase Current... 18 

Current Rectification 

Why A. C. Should be Rectified for Projection, 

390 and 442 

Current Rectifying Device Recommended. 443 

Electrical Action 

Electricity—What Is It?... : . ^ 

Necessary to Understand Electrical Action. 3 

JPplarity.,,,..?... 3 


v 































HANDBOOK OF PROJECTION FOR 

Circuit—Of What It Consists. 3 

Wires Represent Poles of Generator at Distance.... 4 

Live Wires—What They Are. 4 

Positive and Negative—Why One Seeks the Other.. 4 

What Polarity Is and How It Is Measured. 4-5 

How Work Is Performed. 5 

Electricity and the Earth. 5-6 

Positive or Negative Has Affinity for but One 

Thing .6 and 353 

Why Projectionist Must Understand Generators.... 6 

Difference in Direct and Alternating Current.. 13 

Advantages of A. C. from Commercial Viewpoint.. 13-14 

How Alternating Current Acts. 15 

What Is Meant by “Current Frequency”?. 29 

Current Frequency Generally in Use. 15 

Generators May Be Built for Any Frequency. 15 

Low Frequency Objectionable for Lighting. 15 

Low Frequency—Where Preferred. 15 

A. C. Action Diagrammatically Explained.16-17 

Action, Single, Two and Three-Phase Current 

Explained. 18 

Ratio of Transformation—What It Is. 40 

Electrical Terms and Measurements 

Ampere—What Is It and What Does it Corre¬ 
spond to?.19-51 

Ampere Hour—What Is It?. 20 

Ampere Turn—What Is It?. 20 

Amperage—What It Means. 20 

Ammeter—What It Is. 19 

Voltmeter—What Is It? . 48 

Arc Voltage Drop—What It Is. 20 

Number of Watts in a Horsepower. 30 

Number of Watts in a Kilowatt. 31 

Examination 

Examination, Projectionists’ . 888 

Examination Board, Composition of. 888 

Examiners, Competent. 889 

Eye Strain 

Eye Strain—What Causes It. 234 

Lack of Definition (Out of Focus) and Eye Strain.. 235 

Eye Strain Due to Flicker. 234 

Eye Strain Due to Poor Screen Illumination. 236 

Eye Strain and Size of Picture.. 236 

yi 


































MANAGERS AND PROJECTIONISTS 


Eye Strain and Glare Spots.237-238-239 

What Constitutes a “Glare Spot”. 237 

Kinds of Glare Spot. 238 

How to Make Clock Non-Glaring. 238-239 

How to Make Exit Lights Non-Glaring.239 

Film, The 

What It Is. 268 

How It Is Made. 268 

Thickness of Film. 269 

Perforations, Standard; and Film Dimensions. 269 

Damage to Film—What Causes It. 270 

Rain—What Causes It.271-272-273 

Film—Waxing Same. 274 

Film-waxers. 274 

Film—Mending Same.274 to 280 

Film Cement, Eastman. 280 

Film Cement Formulas. 280 

Measuring Film. 292 

Where to Keep Film .288 

Moistening Dry Film . 289 

Film Notching Pliers. 288 

Film, Inspection and Repairs of 

Inspection—Not the Duty of Projectionist.286 

Inspection—Duty of Film Exchange.286 

Inspection—Failure of Exchange to Inspect and Re¬ 
pair Film Dishonest. 286 

Thorough Inspection and Repair Essential to Good 

Projection. 287 

Reason for Poor Exchange Inspection.287 

Ordinary Exchange Inspection as It Is. 288 

Projectionist Should Be Paid for Time Spent on 

Film Inspection and Repair. 288 

Film on Circuit. 288 

Flicker 

Its Effect on the Eye.-234-235 

Is Always Due to Wrong Procedure in Projection... 235 

h 1 ' 1 _ _ I \__ i. - I ) __ 1 ... M M C L aa i i ^ T /x a a n ax lx 1 /x O ^ C 


Fuses 

What Fuses Are For. 107 

Explanation of Fuse Action. 107 

Will Carry Overload. 108 



































HANDBOOK OF PROJECTION FOR 


Why Fuses Protect... 108 

Protect Against Operation of Faulty Circuit. 108 

What Markings Should Be Stamped on Them. 118 

Types Used in Theatres. 108 

At What Point They Should Be Installed. 119 

Cartridge Fuses .. 109 

Ferrule and Knife Blade Contact Fuses. 109 

Ferrule Contact Limited to 60 Amperes. 109 

Pilot Wire of Cartridge Fuses. 109 

How to Tell if Cartridge Fuse Is Blown. 109 

Detailed Description of Cartridge Fuse.108-109-110 

Dimensions Different for Different Voltage.112-113 

Plug Fuses.110-111 

Plug Fuses Limited as to Capacity. Ill 

Plug Fuses Used for Any Service. Ill 

“Boosting” Them.111-114 

Boosting Fuses Very Dangerous. Ill 

Caution Concerning Same. 114 

May Fuse 25 Per Cent. Above Rated Capacity of 

Motor. 114 

Refilling Old Fuses. 114 

Throw Away Old Fuses. 114 

Fusing Projector Circuit. 114 

Proper Capacity for Projector Arc Circuit. 115 

Fusing Projector Circuit When Using Motor Gen¬ 
erator, Rotary Converter or M. A. Rectifier.... 115 

Important to Keep Supply of Fuses on Hand. 116 

Fusing One Side of Circuit in Emergency. 116 

Copper Wire Substitutes for Fuses. 117 

Effect of Faulty Fuse Contacts. 117 

Directions for Testing Fuses. 118 

Fuses for Emergency Light Circuits. 120 

Fuses for Exit Lights. 120 

Double Fusing Projector Circuits. 120 

Projection Room Fuses, Main Service Circuit. 342 


Generators (Dynamos) 


Also see Motor Generators 

Law, Operation of Electric Generator Is Based On.. 7 

Armature—What It Is.. 21 

How Armature Works. 8 

Armature Coil—What It Is. 21 

All Armatures Generate Alternating Current. 8 

Armature, Back End of. 21 

Commutation—How Direct Current Is Obtained_9-10 

Electric Generator, or Dynamo. 11 

Armature Coils Are Interconnected. 11 


viii 









































MANAGERS AND PROJECTIONISTS 


Description of Electric Generator.11 and 21 

What Voltage and Amperage Depend Upon. 11 

How Dynamo Starts to Generate Current. 12 

Brush—What It Is. 22 

Brush Rocker—What It Is. 22 

Field Coil—What It Is.11 and 28 

Permanent Magnet—What It Is.12 and 28 

Residual Magnetism—What It Is. 12 

Magnetic Saturation—What It Is. 12 

Field Rheostat and What It Is For. 28 

Constant Current Dynamo. 25 


Grounds 

Grounds. 352 

Meaning of Term. 353 

Edison Three-Wire System Grounded. 353 

Reason for Grounding Edison Three-Wire System.. 354 
Test Lamp Shows No Light Neutral to Ground.... 355 

Testing for Grounds. 356 

Locating Grounded Coil in Rheostat.358 

What “Ground” in Rheostat Cannot Be Detected by 

Test for Grounds?. 359 

Various Tests for Ground in Rheostat as a Whole.. 359 
Grounding the Projector, and Reason Therefore.... 360 

Effect of Ground in Projection Lamp. 360 

Test for Grounds Daily. 361 

One Prolific Source of Grounds in Lamp. 361 

Method John Auerbach Uses in Testing for Grounds 346 
Permanent Projection Room Ground Wire. 346 


Insulation 


Its Purpose. 80 

Character Varies with Character of Service. 81 

Increased Voltage Demands Higher Insulation Re¬ 
sistance. 81 

Insulating Substances. 80 

Types of Insulation.80-81-82 

No Absolute Non-Conductor of Electricity. 80 

Of What R. C. Insulation Consists.80-81 

Why Coating Wire with Tin Is Necessary with 
R. C. 81 


Why R. C. Wires Have Lower Capacity Rating 


Than Others. 83 

Type of Insulation Permissible in Conduit. 83 

Single Braid R. C. Permitted on Wires Smaller 
Than No. 8. 83 


ix 


































HANDBOOK OF PROJECTION FOR 


Main Difference Between R. C. and Other Insula¬ 
tions. 82 

R. C. May Be Used Instead of Weatherproof. 82 

Where Weatherproof May Be Used. 81 

Where Varnished Cloth and Weatherproof May 
Be Used. 82 

Lamp, The 

See Projector, page 362 and turn to page 369 

Lamp House 

See Projector, page 362 

Lens, Projection 

Elements Projection Lens Consist of. 136 

Function of Projection Lens—What It Does. 126 

Front and Back Factor. 136 

Lens Diameter of Great Importance.147-148 

Testing Lens for Distortion. 148 

Attempting to Alter E. F. of Projection Lens. 150 

Guiding Rule in Reassembling Elements of Lens... 138 

Measuring Equivalent Focus of Projection Lens- 152 

Lens Will Project Different Size Pictures. 150 

Repairing Projection Lenses. 139 

Diameter of Projection Lenses Limited. 139 

Data Necessary When Ordering Lenses. 139 

Range of Focal Lengths Carried in Stock. 140 

Matching a Lens You Already Have. 140 

Markings on Lenses Are Not Accurate. 140 

Angles at Which Light Strikes Surface of Lens. 144 

Light Loss Reduced by Cementing Front Lenses... 144 
Safe Estimate of Light Loss in Projection Lens.... 146 
Results, Other Than Light Loss, of Dirty Lenses.... 146 


Measuring Working Distance. 152 

Important That Interior of Lens Barrel Be Black... 138 
To Calculate Size Picture at One Distance, When 

Size at Another Distance Is Known. 154 

Special Grinding of Lens Cannot Remove Keystone 137 
Bausch & Lomb Lenses, 

Figures 36G, 36GG and Page 159 
Snaplite Lenses—See Figures 36E to 36F. Pages 

147 to 150 

Lenses 

Also see Lens, Projection 

Principal Axis of Lens—What It Is 


126 























MANAGERS AND PROJECTIONISTS 

Difference in Plano Convex, Meniscus and Bi-Con- 

vex Lenses. 168-169 

Conjugate Foci—What It Is. 127 

Working Distance—What It Is.129-152 

Equivalent Focus—What It Is.129-152 

Spherical Aberration—What It Is. 129 

Chromatic Aberration—What It Is. 130 

Meaning of Focal Length as Applies to Simple Lens. 134 

Action of Light Through Lenses. 131 

Correcting a Lens—What It Means. 132 

How Curvature of Simple Lens Is Determined_134-135 

How Lens Forms an Image.133-134 

Why It Is Impossible to Focus Condenser Beam to 

a Point—Figure 30 and Pages.135-136 

To Trace Light Rays Through Lenses. 209 


Light Action in General 

Density of Light at Different Distances..125-161 

Absorption of Light—What It Means. 19 

Actinic Ray—What It Is. 19 

Angle of Incidence—What It Is. 20 

Angle of Reflection—What It Is. 20 

Angle of Projection—What It Is. 20 

Candle Foot, or Foot Candle—What It Is. 23 

Standard Candle—What It Is. 23 

Chromatic Aberration—What It Is. 130 

Critical Angle—What It Is. 26 

Diverging Beam—What It Is. 26 

Diffusion of Light—What It Is.27 and 222 

Refraction—What It Is. 127 

What Controls Amount of Bending of Rays.127-128 

Light Source, The 

Also see Arc, The 

Comparison of D. C. and A. C. Craters. 390 

Comparison of High Intensity and Ordinary Craters. 869 

Using A. C. at Arc for Projection. 390 

Candle Power of Crater.379 and 392 

Data Columbia Positive and Silvertip Negatives.393 

High Amperage Wasteful... 394 

Data Directo Positive and Holdark Negatives.395 

What Happens When Amperage Is Increased.395 

Why 120 Amperes Is Limit of Amperage.395 to 399 


Setting the Carbons. 402 

Testing Side Line of Carbons.. 404 

xi 






































HANDBOOK OF PROJECTION FOR 


Crater Angle. 405 

Maintaining Crater Angle. 408 

How to Find Correct Angle. 409 

License, Projectionists 

Also see “Examination” general remarks concerning same, 884 

Mazda Projection 

Mazda Lamp Projection. 815 

Advantages of Mazda Lamp Projection.842 to 852 

General Remarks.815 to 817 

The Lamp. 817 

How Light Source Is Made Up. 818 

Short Circuiting in Coils. 819 

Blackening of Bulb and Its Effect. 821 

Quality of Light. 822 

Large and Small Diameter Lenses and the Effect... 823 
Relative Light Transmitting Power of Large and 

Small Diameter Projection Lenses.825 

Current Control Apparatus.826 and 855 

Synchronous Converter. 831 

Rheostatic Control. 832 

Using Lamp Setter. 833 

Importance of Filament Alignment. 836 

To Adjust Lamp Filament on Optical Axis. 837 

Plano-Convex Condensing System.852 to 868 

Advantages of Plano-Convex System. 854 

Focusing Mirror Image, Plano-Convex System_867 

Focal Distances, Plano-Convex System. 866 

Mercury Arc Rectifiers 

Principle of Operation. 515 

How Bulb Is Started. 516 

Installation . 517 

General Electric Rectifier .518 to 530 

Old Style General Electric Rectifier.531 to 534 

Trouble Chart . 533 

Westinghouse Rectifier .534 to 543 

Motor Generators 

Also see Current Rectification 

Motor Generator—What It Is. 443 

General Instructions Applying to All Motor Gen¬ 
erator Sets .. .444 to 461 

Location of Set . 444 

xii 


































MANAGERS AND PROJECTIONISTS 


Installation .... 445 

Oiling . 448 

Care of Commutator . 451 

Hertner Transverter .461 to 467 

General Electric Company Motor Generator Com- 

pensarcs .467 to 471 

Westinghouse Motor Generators.471 to 485 

Hallberg Motor Generators.485 to 505 


Wotton Vertical Rexolux Motor Generator ..505 to 514 

Oiling the Projector 

See General Instruction No. 1, page 593, and recommenda¬ 
tions, if any, under instructions on the particular pro¬ 
jector you are using. 

Picture, Distortion of—Keystone Effect 


Distortion Due to Side View and How to Calcu¬ 
late Amount There Will Be. 252 

Distortion Due to Projection Pitch—Keystone.253 

How to Calculate Amount of Distortion. 254 

Safe Guide in Projection Pitch.255 to 256 

How to Make Sides of Picture Parallel. 258 

How to Overcome Out-of-Focus Effect.258 

Why Objects Look Abnormally Thin and Tall.253 

Picture, Size of 

As to Picture Size.243 to 244 

Increase of Light Increase of Picture Size Makes 
Necessary . 245 


Magnification of Defects Increases With Size.... 246 


Practical Projection Optics 

Also see “Light Action in General, and Lens Projection” 

Law of Light . 125 

Refractive Index of Projection Lens Glass. 143 

Light Loss. Dirty Lenses Increase It. 141 

Light Loss. Refractive Index of Glass Affects It- 142 

Light Loss Due to Slide Carrier. 177 

Projector Optical Train Consists of.125 to 126 

Shape of “Spot” and What It Means. 174 

Ratio Light Source Is Magnified In Spot. 175 

Location of Crater Image. 172 

Importance of Size of Spot. 173 

Ghost Zone in Condenser Beam. 177 

Light Source Image Inverted at Spot. 177 

Adjusting Projector Optical Train...... 179 


xiii 






























HANDBOOK OF PROJECTION FOR 


Necessity for Intelligent Application of Data We 

Supply .: • • •;. 180 

Depth of Picture and Evenness of Illumination.... 180 
Impossibility of Evenness of Screen Illumination 
Unless Light Beam All Enters Projection Lens 

181-182-183 

Practical Effect of Unevenness of Screen Illumina¬ 
tion .180 and 183 

Divergent Beam Between Aperture and Lens. 184 

Effect of Divergent Beam Between Aperture and 

Projection Lens .186-187-188-189-190 

Lens Diameters Limited By Focal Length of Lens 184 

Effect of Dirty Lens, Other Than Light Loss. 146 

Diameter of Projection Lens. Its Importance 

148 and 186 to 190 

Lens Tables of Slight Value. 158 

Measuring Focal Length of Lens.151-153 

Beneficial Effect of Spherical Aberration. 172 

Spot. Advantages and Disadvantages of Large One 174 
Effect of Distance of Condenser from Aperture Has 
on Divergence of Beam Between Aperture and 

Projection Lens . 184 

Possibilities For Light Loss Through Divergence 
of Beam Between Aperture and Lens.... 186 to 194 
Universal Method of Ascertaining Condenser Focal 
Length and Aperture Distance With Relation to 

Projection Lens Diameter.194 to 202 

Importance of Correct Selection and Adjustment of 

Projector Optical Train Lenses.202-203 

Give Your Views As to Reducing Condenser Diam¬ 
eter- Under Certain Conditions.203-205 

Is a Very Large Diameter Condenser Practical?.. 205 

Aerial Image. What Is It?. 205 

Revolving Shutter. See “Revolving Shutter,” page 611 
Revolving Shutter and Lens Diameter. 208 


Projector, The 

Standard Projector Aperture, Dimensions of...20 and 608 


New Projectors vs. Old. 329 

Anchoring Projector to Floor. 334 

Lamphouse Ventilation . 362 

Lamphouse Ventilation of Extreme Importance.. 362 

Cause of Poor Lamphouse Ventilation.362-363 

Best Method of Ventilation. 363 

Condenser—see “Condenser, The”. 

Carbons—see “Carbons”. 

Setting the Carbons .402 

Projector Mechanisms, Instructions On.... .592 to 766 


xiv 























MANAGERS AND PROJECTIONISTS 


General Instructions For All Projectors.592 to 626 

Lubrication of Projector Mechanisms. 593 

Intermittent Oil Well Lubricant. 594 

Takeup Tension, Its Importance and Adjustment.. 595 
Dirty Sprockets. Harm They Do. How to Clean 

Them . 596 

Sprockets in Line . 597 

Adjustment of Intermittent Movement. 598 

End Play of Intermittent Sprocket. 601 

Worn Sprocket Teeth. Harm They Do. 602 

Gate Idlers .603 

Gate Tension Adjustment.603 

Emulsion Deposit. To Prevent. To Remove.604 

Worn Aperture Plate Tracks. 605 

Sprocket Idlers. How to Adjust Them.606 

Lining Cam Shaft.606 

Projection Room Reels. 607 

Upper Magazine Tension . 608 

Standard Aperture Dimensions .20 and 608 

Threading in Frame . 610 

Revolving Shutter .611 to 625 

Setting the Shutter. 623 


Power’s Projector, Instructions on Mechanism 

627 to 651 

Power’s Projector, Instructions on Old Style Drive 651 
Power’s Projector, Instructions on New Motor 


Drive . 657 

Power’s Projector, Parts List.659 to 662 


Simplex Projector, Instructions on Mechanism 

663 to 688 

Simplex Projector, Instructions on Speed Control 688 
Proctor Projector, Instructions on Mechanism 

691 to 708 

Motiograph De Luxe, Instructions on Mechanism 

709 to 728 

Motiograph De Luxe, Parts List.728 to 733 

Baird Projector, Instructions on Mechanism.734 to 750 

Baird Projector, Parts List.751 to 753 

Motiograph, 1916 Model, Instructions on... .754 to 766 

Projection, Practical 

Projection. What the Term Includes. 213 

Projectionist, Definition of. 39 

What Depends Upon Excellence in Projection?.. 213 

Range of Knowledge Projectionist Must Have.214 

Projectionist Re-directs Photoplay.214 

Projecti<?n Hampered by Wrongly Made Schedules 215 


xv 






























HANDBOOK OF PROJECTION FOR 


Over-speeding and Its Results. 216 

Correct Speed of Projection.39-217 

Reasons for Necessary Variable Projection Speed 217 

Projection Speed Chart. 215 

Rear Projection—General Data Concerning Same 233 

Overshooting. What It is. 36 

Screen Brilliancy—What Is Meant By the Term.. 43 

Leader and Tail-piece. 284 

Projection Room, The 

Location . 293 

Objections to Great Distance Lens to Screen 

294-295-296 

Front of Balcony Location. 296 

Main Floor Location. 298 

Essentials of Good Projection Room.300-301-302-303 

Projection Room Door. 304 

The Floor . 304 

Wall Construction . 306 

Conduit—Building Into Walls. 306 

Ports . 306 

Locating Ports .307 

Filling in Ports. Figure 85. 309 

Size of Observation Ports. 309 

Glass Over Ports. 310 

Sliding Shutter for Observation Port. 310 

Shadow Box for Port. 311 

Small Ports and the Law. 312 

Port Fire Shutters.312 to 316 

Ventilation .317-318-319 

Projection Room Equipment.319 

Projection Room Closets. 320 

Running Water—Toilet . 321 

Projection Room Chair. 321 

Projection Room Reels. 322 

Projection Room Supplies. 327 

Records Should Be Kept. 329 

Proof That Too Great Economy in Supplies Does 
Not Pay . 329 

Projection Room Lighting 

Lighting of Room of Great Importance. 344 

Connection Between Projection Room Illumination 

and Screen Results. 344.345 

Lighting for Rooms With Small Observation Ports 345 

Two Circuit System Used in England. 345 

Burning of Incandescents While Projecting Should 
JBe Forbidden .,. 345 

xvi 





































MANAGERS AND PROJECTIONISTS 

Projection Room—Wiring Same 

Size of Wires Necessary. 338 

Should Figure Voltage Drop?. 339 

General Lay-out of Projection Room Switchboard 340 

Balancing the Load. 341 

Connecting Motor Generators, Economizers, etc.... 341 

Incandescent Circuits . 344 

Ground Wire . 346 

Projector Circuits . 348 

Double Throw Connection for Projector Circuits.. 348 

Trouble Lamp . 348 

Projector Circuits—How They May Be Run. 348 

Inclosure of Switches. 348 

Double Throw Connection of Projector Circuits. 348 

Transformer—Rheostat Connection, When Used... 349 
Connecting to Two Sources of Supply. 350 


Rectifiers, Mercury Arc 

See Mercury Arc Rectifiers 

Reels 

Construction) of Reels... 281 

Size of Reels . 282 

How to Calculate Footage a Reel Will Hold. 283 

Filmfast Reel . 323 

Simplex Automatic Signal Reel. 324 

Projection Room Reels.281, 282 and 322 

Resistance 

Figuring Resistance of Arc. 57 

General Discussion Thereof. 60 

Resistance of Metals. 65 

Resistance and Temperatures. 65 

Temperature Co-efficient . 66 

Normal Temperature . 66 

Properties of Metals. 67 

Loss Through Resistance. 68 

Amount of Resistance Permissible in Circuit. 69 

Mil Foot Standard of Resistance. 73 

To Calculate Resistance When Size and Length of 

Wire is Known. 73 

Calculating Resistance of Copper Circuit. 73 

Figuring Voltage Drop of Circuit.... 74 

xvii 
































HANDBOOK OF PROJECTION FOR 


Resistance as Applies to Projection Circuit 

Why Resistance Is Necessary In Projection Circuit 413 

Variable and Fixed Resistance Rheostats. 415 

Heating of Rheostat . 417 

Rheostat Repairs . 418 

Insulate Your Rheostats. 419 

Location of Rheostats. 420 

Necessity for Examining Connections Frequently.... 421 

How Additional Resistance Coils May Be Added.. 421 

Objections to Large Grid Rheostats. 422 

Temporary Repairs If Coil or Grid Breaks. 423 

Rheostat Connections . 423 

Series Connections . 423 

Multiple (parallel) Connection . 424 

A.C. and D.C. Rheostats—No Such Thing. 427 

Rheostat Connections and Resultant Amperage.... 429 

Adjustable Rheostat—What It Is. 432 

Disassembling Wire Coil Rheostats.435 

Rheostats for Road Use. 436 

A New Kind of Rheostat. 437 

Rewinder, The 

Rewinder, The . 332 

Rheostats 

See Resistance as Applied to Projection Circuit 

Screen, The 

The Sole and Only Function of the Screen. 219 

Impossible to Judge Relative Merit of Screens by 

Looking at Them In Different Theatres.219-220 

Picture Light, What It Is. 219 

Various Things Which May Alter Screen Brilliancy 

Per Ampere of Current Used. 220 

Only Way Reliable Comparative Test Can Be Made.. 220 
Be Cautious as to Accepting Statements of Sales¬ 
men . 220 

Projectionist Should Study Screen Surfaces. 221 

What Exhibitor Should Do Before Purchasing 

Screen . 221 

Reflection, Diffuse, Semi-Diffuse and Regular. 222 

Visible Roughness of Screen Unnecessary. 223 

Interfering Light a Serious Matter. 224 

Test Screen for Stray Light. 224 

Distribution of Reflected Light. 225 

White Wall Screen . 226 

xviii 






























MANAGERS AND PROJECTIONISTS 


Cloth Screen .226 

Painted Screen . 227 

Kalsomine Screen Surface.229 

Kalsomine Surface—How Often It Should Be 

Cleaned . 229 

Testing Screen Surface as to Its Condition.230 

Neat Cement Screen Surface. 230 

)TE: I1 was found too late for correction in the text that 
the correct name is “white” cement, instead of “neat” 
cement. 

Glue Sizing for Cloth Screen. 230 

Metalized Screen Surfaces.230 

Chalk Screen Surface. 231 

Metal Surface Screen—Tendency to Discoloration 231 

Metal Surface Screen—Difficulty of Making. 231 

Mirror Screens . 231 

Translucent Screens . 232 

Ground Glass Screens Best for Rear Projection.233 

Concave Screen. Possible Advantage in Its Use.. 233 

Height of Screen Above Floor. 234 

Screen Must Have Flat Surface. 239 

Location of Screen With Relation to Lens. 240 

Border Surrounding Picture.240-241-242 

Screen Surroundings Non-gloss. 243 

Size of Picture. See “Picture, Size of.” Page-243 

Tinted Screen Surface. 246 

Locating Screen at Front of Hose. 247 

Screens for Traveling Exhibitors. 249 

Stretching and Mounting the Screen-249-250-251-252 

Characteristic of Screen Surfaces.258 to 267 

Classification of Surfaces . 260 

Screen and Viewing Angle.261-262 


Shutter, Revolving 


Is an Integral Part of Optical System.206 

Necessity for Shutter Limits Lens Diameters. 206 

Correct Position for Shutter. 206 

How Correct Position is Found.206-207 


Reason for Locating Shutter at Aerial Image.... 207 
Large Lens Diameter Calls for Wide Master Blade 208 


Slides 

Announcement .337 


xix 






























HANDBOOK OF PROJECTION FOR 

Speed Indicators 

Power’s Speed Indicator. 768 

Hallberg’s Speed Indicator. 770 

Robbin’s Speed Indicator. 772 

Spotlight, The 

Spotlight . 794 

High Intensity Spot. 796 

Lenses for Spotlight. 799 

Stereopticon, The 

Kind Now Required for Projection Rooms.800 

Slide Size . 800 

Slide Carrier Loss. 801 

Combination Projector .. 802 

The Dissolver . 803 

Dissolving Shutter . 805 

Dissolving With Two Combination Projectors.... 806 

Registering the Lenses . 807 

Dissolving Carrier for Single Stereopticon. 808 

Handling Slides—Right Way to Do It. 810 

Making Slides for Use in Theatre. 811 

Repairing Slides .810 

Switchboards 

Rules Applying to Installation of Switchboards.... 97 
For Information Concerning Installation of Switch¬ 
boards Apply to . 106 

As to Locating Same in Projection Room. 98 

Necessity for Understanding Switchboards. 99 

Circuits Main Board Should Carry. 99 

Fuses Main Board Should Carry. 99 

Panel Boards . 100 

Exit and Emergency Circuits Not Connected to 

Main Switchboard . 103 

Built-up Boards .103-106 

Stage Switchboard . 104 

Types of Fuse Used on Stage Board. 106 

Fuses Stage Board Should Carry. 106 

Importance Stage Board in Good Condition. 106 

Stage Board Handled by One Man Only. 106 

Switches 

Types Used in Theatres. 92 

Care Switches Should Have.92 and 96 

xx 


































MANAGERS AND PROJECTIONISTS 

Right Way to Install.92-93 

Single Throw and Single Pole, What It Is. 44 

Double Throw and Double Pole, What It Is. 27 

Triple Pole Switch, What It Is. 47 

Inclosed Switch, What It Is. 94 

Locating Switches, What Should Govern. 94 

Emergency Light Switches Not on Board. 94 

Projection Room Switches, Locating Same. 95 

Single Pole Switches in Theatres. 95 

Triple Pole Switches, Where Used. 95 

D. P. D. T. Switches, Where Used. 95 

Markings Must Be Stamped on Some Part of All 

Knife Switches . 96 

Different V.ltage and Amperage Require Different 

Switches . 96 

Faults to Look for in Your Switches. 96 

Metal Switch Cabinet, When Required. 96 

Stage Switches Should'Be Marked. 106 

Polarity Switch . 350 

Tools 

List of Tools Necessary. 335 

Hand Bellows Necessary. 335 

Blow Torch for Light Work. 335 

Keep Tools in Order. 337 

Transformers 

Transformer, The . 544 

Electrical Action of Transformer. 544 

Two Types of Transformer. 545 

Efficiency of Transformer. 547 

Transformer Core, What It is. 547 

Ratio of Transformation . 547 

Relative Position of the Coils. 549 

Low Voltage Transformers. 549 

Permissible Temperature of Transformer. 550 

Choke Coil, What It Is.24 and 550 

Multiple Connection of Transformers. 551 

General Electric A. C. to A. C. Compensarcs.552 to 553 

Hallberg Economizers .553 to 557 

Power’s Inductor .557 to 558 

Wires 

Also see Wire Splices and Terminals 

Carrying Capacity of. 69 

Wire Capacity Tables I and IA.70-71 

How to Calculate Area of Cross Section. 77 


xxi 







































HANDBOOK OF PROJECTION FOR 


How to Calculate Capacity of Wires. 77 

How to Figure Voltage Drop.75-76-77 

To Calculate Voltage Drop of Circuit. 75 

To Calculate Size to Carry Given Amperage at 

Given Voltage Drop. 76 

B & S Wire Gauge. 78 

Micrometer Caliper for Measuring Wires. 78 

Relative Carrying Capacity of Aluminum. 70 


Wire Splices and Terminals 


Terminal Lugs. All Wires Should Have Them.... 121 
Terminal Lugs. How Attached to Wires. 121 


Power Wasted in Poor Joints Registered on Meter 122 

Wire Splices . 123 

What Underwriters’ Rules. Require as to Splices.. 123 

Proper Method of Removing Insulation. 123 

Proper Method of Soldering Wire Splice. 123 

Proper Method of Insulating Splice. 123 

Solder Flux . 124 

Terminal Lugs For Hot Places. 124 

Wire Systems 

Two-wire System . 84 

Three-wire System . 85 

To Calculate Economical Operation of Circuit.... 76 

True Negative and Positive of 3-wire System. 86 

Neutral Both Positive and Negative. 86 

Advantages of 3-wire System. 87 

Balanced Load on 3-wire System. 88 

How to Test Balance of Load. 91 

Why Balanced Load is Important to Power Com¬ 
pany . 88 

Effect Removal of Neutral Fuse.88-91 

Connect Mercury Arc Rectifier to Outside Wires.. 89 
Use Motor of Voltage of Outside Wires of a 3- 

wire System . 89 

Use Economizer of Voltage of Outside Wires.... 89 
As to Connecting to Outside Wires When Taking 

Current Through Rheostats. 88 

Edison Neutral Always grounded.353 and 354 


Miscellaneous 


Automatic Curtain Machine. 873 

Bells, Electric. 895 


xxn 































MANAGERS AND PROJECTIONISTS 


Blow Torch for Light Work. 336 

Coloring Incandescent Lamps.903 

Decimal Equivalents. 906 

Dowser, Weaver. 870 

Fahrenheit and Centigrade Scales Compared. 907 

Film Splicer.277-334 

Film Storage Cabinets. 330 

Fire Proofing Solution. 249 

Library for Projectionist. 904 

License, Projectionist. 883 

Meters, Electric . 891 

Projectionists’ Report .880 

Reflective Power of Different Surfaces. 907 


xxiii 

















Important Foreword 

M ODERN projection covers such a huge field that to 
treat it and all things allied to it in exhaustive detail 
would require a book of very much more than a thou¬ 
sand pages. Such a volume, besides being expensive in price, 
would be unwieldy, easily injured and in every way awkward. 
Dividing the work into two or more volumes has very serious 
objections, hence, in what we believe to be the best interests 
of all concerned, the following plan has been adopted for 
keeping both size and price within reasonable limits. 

In dealing with both electrics and optics there are many 
things which need not necessarily be understood in large 
detail by the projectionist, and which comparatively few 
would study, even though they be set forth in detail in this 
book. In such matters we have decided to give the essential 
facts as briefly as may be and refer our readers to other 
readily available standard text books for details. 

We will, however, so far as possible, confine such references 
to books which the projectionist is likely to already own, or 
which he may consult in almost any public library. We be¬ 
lieve our readers will heartily approve this plan, because, 
while causing no hardship, it will reduce the handbook both 
in bulk and price. 

The “Hawkins’ Electrical Guides,” by Hawkins, and 
“Optic Projection,” by the Professors Gage, will be used 
for reference wherever possible, because these most excellent 
works are already in the library of many projectionists and 
should be owned by them all. 

Quite a little of what may seem repetition will be found in 
this book. This is because it is found necessary to mention 
certain things in several different connections, and to do so 
by cross reference would not always serve the best pur¬ 
pose. There is no duplication except in cases where the 
author believed duplication would serve the best interests of 
the users of the book. 


THE AUTHOR. 








Projection in the Modern Moving 
Picture Theatre and What 
It Entails 

M ODERN motion picture theatres are indeed temples of 
beauty. In many cases they represent an outlay 
reaching well into six figures, the income from which 
depends very largely upon the excellence of what paying pa¬ 
trons see upon the screen. Great producing companies have 
established reputations which have drawing power at the box 
office. The same is true of what we term “stars.” The expert 
work of cameramen, and those others who contribute to the 
truly wonderful photographic results found in modern films, 
all have their share in popularizing the motion picture as a 
salable form of theatrical amusement. A good orchestra has 
considerable drawing power. 

Fine seats, good ventilation, beautiful light effects and deco¬ 
rations all lend aid in the sale of tickets, but the fact remains 
that even though a theatre have all these things, still, if there 
be anything less than high class, expert work in the projec¬ 
tion room, the shadow forms of the artists will not appear to 
best advantage, the photography, though wonderfully beauti¬ 
ful in the film itself, will be only ordinary on the screen, and 
in many other ways the show will be made less pleasing, with 
the result that the box office income will inevitably suffer. 

The following is put forward as a flat statement of amply 
proven fact: Given a free hand, unhampered by unreasonable 
schedule restrictions, limited amperage or penuriousness in 
the matter of projection room operating expense, the care¬ 
ful, painstaking projectionist who is equipped with expert 
knowledge of his profession, can “put over” a production of 
mediocre merit, sending forth an audience at least fairly well 
pleased and of mind to come again; whereas the slovenly, 
careless projectionist, or the projectionist not equipped with 
expert knowledge, although otherwise equally unhampered, 
will either cause the same subject to fall flat, or will give a 

1 


2 


HANDBOOK OF PROJECTION FOR 


less satisfactory performance with a production of far 
superior merit; and since inferior screen results must inevi¬ 
tably react unfavorably on future ticket sales, it follows that 
careful work and expert projection knowledge has direct value 
to the box office through increased patronage of the theatre. 

Not only is this true, but the well informed projectionist is 
in a position to effect material saving in projection room ex¬ 
penditures, both in the matter of daily operating expense and 
in better and longer service of equipment. This latter item 
may be a very large one indeed, if we include the possible 
saving in film damage through intelligent adjustment of the 
machine tensions and intelligence in the matter of rewinding 
and handling of film, remembering that all film damage must, 
in the last analysis, be charged back to the theatre in the 
form of increased film rentals made necessary by added over¬ 
head expense to exchanges through frequent purchase of 
prints to replace those ruined by unintelligent handling. 

With these facts in view we may readily understand the im¬ 
portance attached to the study of the details of his profession 
by the projectionist, and this book is designed primarily to 
supply detailed information, in plain words and understand¬ 
able form, concerning those many things the competent, 
modern projectionist should and must know. 

We shall labor hard to produce the best book possible, 
but have no hope of attaining perfection. The work is a large 
one and it is inevitable that some errors—minor ones only, we 
trust—will be found in its text. These we ask you to view 
with charity, remembering that few things in this world of 
ours are perfect. 

PRACTICAL THINGS OF GREATEST IMPORTANCE.— 

This book, like its predecessors, is designed for the use of 
practical men, hence, as in past editions, we shall pay very 
much more attention to practical things and understandable¬ 
ness, than to absolute technical correctness. Strict technical 
correctness, especially in matters electrical and optical, often 
involves the use of a maze of words and technical terms, many 
of which latter could not possibly be understood by the 
ordinary man without such long-winded explanations that the 
novice would become confused and discouraged. 

Therefore, when we are able to make a point sufficiently 
clear for all practical purposes merely by the sacrifice of some 
unimportant point of technical correctness, we shall unhesi¬ 
tatingly do so, believing that course to be, all things consid¬ 
ered, best. 


MANAGERS AND PROJECTIONISTS 


3 


Electrical Action 

I N order to arrive at a comprehensive knowledge of elec¬ 
tricity, one must first understand the underlying principles 
which govern its action. It is absolutely imperative that 
the projectionist have at least a good working knowledge of 
electrical action, because he will be put in full charge of ap¬ 
paratus for generating and using current, which devices will 
operate safely and with high efficiency, or with low efficiency 
and perhaps unsafely, exactly in proportion to the expert skill 
and knowledge he is able to make use of in their adjustment, 
care and handling. 

We will first try to convey an understanding of the one 
basic, underlying principle upon which all electrical action 
is based, always remembering that electricity and magnetism 
are two entirely separate and distinct things, notwithstanding 
statements of some authorities to the contrary. 

POLARITY. —Polarity is the very foundation principle 
upon which all electrical action is based. Precisely what 
electricity is, no living man knows. Eminent scientists differ 
widely in their views as to the cause of the phenomenon. Some 
authorities claim it to be a “molecular bombardment,” while 
others hold it to be something entirely different. With such 
arguments the practical man has little interest. At best they 
represent little more than abstract theories. They have no 
importance as applied to the work of projection. 

We may not know the precise nature of the thing which 
does it, but we do. know that if we touch a “live” positive wire 
to a negative wire attached to the same generator, there will 
be a flash and a shower of sparks. We also know that by 
Connecting these two wires through certain devices, such as 
motors and lamps, instead of an uncontrolled flash and shower 
of sparks we can and do get light, heat or power. In other 
words we can make the electric force work for us in its pas¬ 
sage from positive to negative. 

So far as electric action is concerned, every electric circuit 
consists of just two wires—a positive and a negative. True, 
there may appear to be more, as in the three-wire system, but 
when analyzed we find that the additional wire or wires 
merely operate to form additional complete circuits, which 


4 


HANDBOOK OF PROJECTION FOR 


may either be used singly or together, as will be fully ex¬ 
plained in the proper place. 

One positive and one negative conductor constitutes what is 
called a “circuit.” Every electric generator (dynamo) and 
every battery has a “positive” and a “negative” pole. In order 
that the power of the generator or battery be available for 
use at a distance, we attach a wire to each of these poles. 
These wires become a part of and represent the poles of the 
generator or battery, so that connecting a lamp or motor 
to them at any portion of their length is the same as attach¬ 
ing it to the actual poles of the machine itself, modified only 
by the fact that resistance is offered by the wires to electric 
action which for a given size of wire increases as the length 
of the wire increases, as will be fully explained under the 
proper heading. 

When disconnected from the generator, or when the gen¬ 
erator is not running, these wires are precisely the same as 
any ordinary wire. They are “dead.” But the instant they 
are connected to the poles of a working generator or battery 
they become “live wires,” the positive wire becoming charged 
with an electrical energy which, measured in “volts,” is 
called “voltage” and corresponds to pressure in a steam boiler. 
Steam confined under pressure in a boiler seeks to expand 
its volume, since by so doing its pressure is reduced. When 
it escapes into the open air its pressure is reduced to at¬ 
mospheric pressure, hence it seeks always to so escape. 

Electricity under pressure, or tension, in the positive wire 
seeks to escape into the negative wire for precisely the same 
reason—its pressure or tension is reduced to zero by so doing. 

Technical electricians will no doubt feel inclined to criticise 
our last statement, but while they may do so from the purely 
technical standpoint, what we have said describes what 
actually apparently takes place in practice, and it is under¬ 
standable. Those who care to go into fine-spun theories will 
find books in plenty which will carry them as far as they may 
wish to go into a very maze of it, but when they have done, 
they will only be able to tell us, in technical language, what 
for all practical purposes amounts to precisely what we have 
just said. Our concern is to make you understand the 
practical effect of what takes place between positive and 
negative. If we accomplish that result we are well satisfied. 

The affinity of positive for negative—the desire, if you 
please, of the positive energy to become negative—is what we 
term “polarity.” It represents difference in electrical pres- 


MANAGERS AND PROJECTIONISTS 

sure as between positive (+) and negative (—). It is measured 
in volts. 

HOW WORK IS PERFORMED.— Steam under pressure 
generated by confining it in a boiler, seeks to lower its pres¬ 
sure by expanding in volume. We allow it to enter the cylinder 
of a steam engine in which is a movable piston. On one side 
of the piston is the pressure of the steam, and on the other 
only the pressure of the air, which for our purpose represents 
zero. In seeking to expand its volume, and thus reduce its 
pressure, the steam will shove the piston ahead of it to the 
end of the cylinder, pulling with it the load attached to it, 
thus generating power. 

In doing this the steam itself is not consumed. It still exists, 
having been discharged into the open air, but its pressure has 
been consumed. Steam is merely the medium, the compres¬ 
sion of which stores up power. It acts precisely as does a 
coil spring. Compress the spring and you will have stored- 
up power, which will be available until the spring has again 
expanded to its former state, whereupon, while the spring 
itself remains, the power has all been expended and is gone. 

We cannot see electricity. The light we see in a lamp is 
not electricity itself, but a product of its power. We cannot 
weigh it. Apparently it has no weight. We cannot 
feel it, except in the form of a “shock,” which again is not 
electricity itself but a product of its power. We do, however, 
find its action to be almost precisely the same as that of steam 
or water under pressure, so that we may readily use these as 
a basis for comparison. 

Apparently, as already set forth, electricity exists under 
pressure on one wire, the positive, and apparently it loses 
its pressure in the act of entering the negative wire—the 
act of becoming negative—hence, since pressure is power and 
pressure is consumed in passing from positive to negative, it 
follows that power is generated when current passes from 
positive to negative and this power is made available for use 
by means of what amounts to an electric engine, one side 
(pole) of which is connected to positive and the other to 
negative. The particular power generating device may be a 
lamp, by means of which light is produced, a motor by means 
of which pulling power is made available, or it may be a 
heating coil. In either case electricity is made to do a useful 
thing, hence its power is turned into useful channels. 

THE EARTH AND THE POWER SOURCE.— There is a 
mistaken idea entertained by many, that electricity seeks to 


6 


HANDBOOK OF PROJECTION FOR 


escape from the wires into the earth. This is not true, except 
insofar as the earth offers a path for the current from positive 
to negative. Let it be clearly understood that: 

There is absolutely no electrical affinity of the positive wire 
of a battery or dynamo for anything else except a wire at¬ 
tached to the negative pole of the same battery or generator, 
except in cases where two or more batteries or generators 
are so connected that they, in effect, form one power source. 

Set two separate 5,000 volt generators operating, and you 
may, with perfect safety, bring the positive of one into direct 
contact with the negative of the other. The result will be 
exactly the same as though two dead wires were brought into 
contact. 

Thoroughly insulate a 10,000 volt generator from the 
ground, including all the wires and apparatus attached to 
it, and you may with perfect safety stand with your bare 
feet on wet ground and handle either the raw (uninsulated) 
positive or negative wire separately. But if the positive or 
negative be “grounded,” and you touch the wire of opposite 
polarity, the current would leap through your body into the 
ground and through the ground into the other wire. It does 
not necessarily follow, however, that when both wires have 
current carrying connection with the ground, the current will 
always pass from positive to negative, because the “ground,” 
as it is called, may have such high resistance that the pres¬ 
sure cannot force the current through. 

HOW ELECTRICITY IS GENERATED.— In a very large 
percentage of theatres the projectionist is placed in direct 
charge of an electric generator. It is therefore essential that 
he not only understand its handling, adjustment and care 
from the mechanical viewpoint, but that he also have accurate 
knowledge of its electrical action and the theory upon which 
it acts in the generation of electric energy, since 
NO MAN CAN INTELLIGENTLY AND EFFICIENTLY 
HANDLE ANYTHING WHICH HE DOES NOT THOR¬ 
OUGHLY UNDERSTAND, and the more a man knows about 
the thing he is handling the betteT service he can cause it to 
give. 

Fill a glass jar of any convenient size two-thirds full of 
water, to which add ordinary sal ammoniac, procurable at any 
drug store, in the proportion of one pound to the gallon of 
water. In this solution suspend a sheet of copper having an 
area of say twenty square inches on each of its two sides. Near 
to, but not in actual contact with the copper, suspend a piece 


MANAGERS AND PROJECTIONISTS 


7 


of zinc of approximately the same superficial area, and the 
whole will constitute the simplest form of electric generator 
known, the assemblage constituting what is known as a “wet” 
battery. If we make electrical connection between the copper 
and zinc of such a battery, current, generated by chemical 
action, will flow from copper to zinc, the former being posi¬ 
tive (+) and the latter negative (—). A well proportioned 
battery of this sort will generate about one volt pressure and 
several amperes of current while it lasts. 

In theory it would be possible to join sufficient of these bat¬ 
teries to produce almost any desired voltage and amperage, 
but in practice this would be impractical. The use of gen¬ 
erating batteries is almost entirely confined to light work, 
such as the ringing of bells and buzzers, the telegraph and 
like service where comparatively little energy is required. 

For power purposes we depend upon the dynamo, or 
“generator,” as it is usually termed. The dynamo depends for 
its action primarily upon magnetism, and the generation of 
electric energy in the armature of a dynamo is based upon 
the following law: 

“If an electric conductor in the form of a closed circuit be 
moved in a magnetic field in such a way that lines of force 
are cut, a current of electricity will be generated therein, 
which same will flow in a direction at right angles to the 
line of motion.” 

See Hawkins’ Electrical 
Guides, Vol. 1, Pages 125 
to 136, for a detailed ex¬ 
planation of this law and 
its operation. 

In Fig. 1 we see the 
diagrammatic representa¬ 
tion of the simplest pos¬ 
sible form of electric 
dynamo. N and S are re¬ 
spectively the north and 
south poles of a perma¬ 
nent magnet, between and 
around the poles of which 
flow magnetic lines of 
force, represented by the 
dotted lines. Within the 
magnetic field thus formed 
is copper wire A—B, bent 




































HANDBOOK OF PROJECTION FOR 


as shown, one end being attached to flat-faced metal ring C, 
and the other end to a similar ring, D. On the face of each 
of these rings, and in electrical contact therewith, rest metal 
brushes J and K. Wires E and F, which represent an outside 
circuit, connect respectively with brushes J and K. It will 
thus be seen that wire coil A—B, through ring C, brush K, 
wire E, lamps L, wire F, brush J and ring D, forms a com¬ 
plete electric circuit. 

HOW ARMATURE WORKS.— Now if by means of crank G 
we rotate coil A—B in the direction indicated by arrow O, 
coil side A will pass down and side B up through the mag¬ 
netic field, cutting across lines of magnetic force in so doing. 
This will (see law before quoted) generate an electric im¬ 
pulse (current) which will, under the conditions, flow through 
the coil, rings, brushes and circuit in the direction indicated 
by arrows M and P. 

ARMATURES GENERATE A C. —And now a step further. 
In Fig. I we assume crank G to rotate in the direction indi¬ 
cated by arrow O. Under that condition the current will flow 
toward brush K, but as the coil is rotated the electric impulse 
becomes weaker, since the coil sides travel more nearly in 
the direction of the lines of force, hence cut less of them, until 
finally side B stands directly over side A, and both are travel¬ 
ing in the same direction as the lines of force, therefore, cut¬ 
ting none of them, so that there is no electric ' impulse 
generated. 

At this point the wires are “dead.” There is no voltage, 
hence no current. But as we rotate the coil still further, the 
wires again begin to cut across the lines of force, and the 
electric impulse is revived and becomes stronger until side 
B reaches the position formerly occupied by side A, when 
the voltage is again at maximum. But since the current 
always flows in the same direction with relation to the magnet 
poles (see arrows L and M) its direction has now been re¬ 
versed in the coil itself, and it flows into brush J, instead of 
brush K, hence around the circuit in the opposite direction. 

Remember that the current within the magnetic field always 
flows in the direction of arrows L and M and that the sides 
of the coil are constantly exchanging their positions' as the 
coil is rotated, hence the current in the coil and circuit is 
reversed with each half turn of the armature, or in multipolar 
machines, every time a coil passes through the field of one 
of the magnetic poles of the machine. 


MANAGERS AND PROJECTIONISTS 


9 


HOW DIRECT CURRENT IS OBTAINED.— Current flow¬ 
ing continuously in one direction, called “Direct Current” 
(D. C.), is obtained from armatures which produce alternating 
current (A. C.) by means of what is termed “commutation,” 
as follows, it being understood that we only intend to explain 
the principle involved. To set forth in detail the intricacies of 
of actual practice would require many pages of text, as well 
as many very complicated illustrations. 



In diagram A, Fig. 2, we see armature coil A—B and a com¬ 
mutator ring split into two sections, E and F, to each section 
of which an end of coil A—B is attached. Resting upon and 
in electrical contact with the “commutator” thus formed, are 
brushes C and D, to which outside circuit G is connected, as 
shown. 

Remembering what has already been said about the direc¬ 
tion of flow of the current in armature coils, and assuming 
it to be in the direction of the arrows, we readily see that 
under the condition shown in diagram A it will flow into com¬ 
mutator section E, out to the circuit through brush C, and 
back through brush D. But when the coil has been rotated 
until coil side B is in position formerly occupied by side A, 
as shown in diagram B, the current will then flow into com- 


























































10 


HANDBOOK OF PROJECTION FOR 


mutator section F instead of commutator section E; but since 
brush C now rests on commutator section F instead of E, the 
current, while reversed in the coil itself, will still flow in the 
same direction over the outside circuit, so that we shall have 
“direct current” everywhere except in the armature of the 
dynamo itself. 

* This is called “commutation.” Please understand that in 
Fig. 2 we illustrate the principle involved in commutation only. 
In modern dynamo armatures there are many coils and com¬ 
mutator sections, bars or segments, as they are variously 
called, but regardless of complications the principle involved 
is exactly what we have described. See Hawkins’ Electrical 
Guides, Vol. 1, pages 171 to 180, for a detailed description of 
the action. 



Figure 3 
























MANAGERS AND PROJECTIONISTS 


11 


We believe a careful study of the foregoing will enable 
our readers to understand how current is generated (we use 
the word “current” for convenience; electromotive force would 
be more nearly technically correct, but current is expressive, 
readily understood and short) in a dynamo, how it gets from 
the armature to the outside wires, and the method by which 
it is changed from A. C. to D. C., which is all we may reason¬ 
ably be expected to accomplish along these lines in the lim¬ 
ited space available for a discussion of the subject in a work 
of this kind. Students desiring to examine into the matter in 
greater detail may do so by consulting the references we have 
provided. Matter helpful to an understanding of commuta¬ 
tion will also be found in Hawkins’ Electrical Guides, Vol. 2, 
pages 237 to 243. 

In studying commutation one very important thing to 
remember is that in practice all armature coils are intercon¬ 
nected with each other through the commutator. Unless this 
point is understood, the student is apt to be sadly puzzled 
as to how there can be any connection between positive and 
negative brushes located at opposite sides of the commutator, 
when the ends of individual coils may connect to adjoining 
commutator bars. 

Fig. 3 illustrates what is known as a “two pole, direct cur¬ 
rent, shunt wound generator,” or dynamo. N and S indicate 
respectively the north and south poles of field magnet A. 
F—F indicates the field winding, which we see coiling around 
the upper or bowed part of the magnet. B is the armature 
around and through which pass lines of magnetic force gen¬ 
erated by the field magnet. C is the commutator, D—D the 
brushes, E—E the wires leading to the outside circuit and G 
the movable lever by means of which the “field rheostat” is 
adjusted. 1, 2, 3 and 4 are the coils of resistance wire forming 
the “field rheostat.” 

The voltage and capacity of the machine described will 
depend, within certain limits, upon (a) the number of lines of 
magnetic force passing through the armature, or in other 
words, the strength of the magnetic field, or in still other 
words, the density of magnetic flux per square inch of area 
of the surface of the pole pieces of the magnet which lies 
next the armature, (b) Number of turns to each armature 
coil and number of coils the armature carries, (c) Rotary 
speed of armature, each of which items has directly to do 
with the number of lines of magnetic force which will be 
cut per second. 


12 


HANDBOOK OF PROJECTION FOR 


Of course, it is understood that other things, such as the size 
and winding of the magnets, kind of armature core et cetera, 
have much to do with the ultimate performance of the ma¬ 
chine, but we are merely explaining to you the principle upon 
which the generator operates, which, with some variations in 
methods, is always the same. 

HOW CURRENT GENERATION IS STARTED.— The 
magnet of the type of dynamo shown in Fig. 3 is a “perma¬ 
nent” magnet, meaning that it does not become entirely 
demagnetized when the armature comes to rest. In effect, 
when lying idle it is just an enormous horse-shoe magnet, much 
the same, except for its size, as the horse-shoe magnets that 
children play with. The magnetism retained when the machine 
is at rest is called “residual magnetism.” It is very much 
too weak to enable a dynamo to build up and maintain a com¬ 
mercial voltage. The most we might hope to accomplish by 
its use would be to generate perhaps ten volts’ pressure. 

Examining Fig. 3 we see that wire F—F coils around the 
upper part of magnet A. It may connect either directly to 
brushes D—D or to lines E—E a short distance from them. 
In other words, coil F—F and the armature form a complete 
circuit, which but for field resistance H would be a short cir¬ 
cuit, and is in fact a short circuit when lever G is in position 
shown. Coil F—F forms what is known as the “shunt field 
circuit” and the generator shown is a “shunt wound” ma¬ 
chine. 

It is a well known fact that if a current of electricity is 
passed through a wire wound upon a fnagnet in the way wire 
F—F is wound, the magnet will have its power increased, and 
that the power of the magnet will increase proportionately 
as the current is increased until the point of “saturation” 
(iron is said to be saturated with magnetism when the point 
is reached where it will receive no more) is reached. 

Bearing the foregoing in mind, a dynamo starts generating 
electro-motive force as follows: First having placed lever G 
in the position shown, which “cuts out” or eliminates all the 
resistance of the field rheostat, the switch connecting wires 
E—E with the outside circuit is opened, so that all current 
generated must flow around shunt circuit F—F, there being 
no place else for it to go. Power from an engine or motor 
is now applied and armature B is rotated at high speed, its 
coils cutting lines of magnetic force in the weak field of 
residual magnetism. This immediately creates a slight electro¬ 
motive force, the current resulting from which flows around 


MANAGERS AND PROJECTIONISTS 


13 


shunt field F—F, thus slightly strengthening the magnet, 
which instantly increases its magnetic flux so that the arma¬ 
ture wires cut more lines of force, which in turn strengthens 
the current flowing over the shunt field. 

This process continues until the normal voltage of the ma¬ 
chine is reached, whereupon the switch connecting with the 
outside circuit may be closed, thus connecting the machine 
with its load, and lever G adjusted, until the resistance of the 
field rheostat limits the shunt field current flow to the value 
necessary to maintain the magnetic field at the strength re¬ 
quired to maintain the desired voltage. 

Modern dynamos for the most part have more than two 
poles, but that fact does not in the least alter the action as 
before set forth. The added poles merely serve to secure the 
same effect with a lower armature speed and with a less 
massive machine. 

DIRECT AND ALTERNATING CURRENT.— Direct cur¬ 
rent, also known as “continuous current” (though the term is 
not always correctly applied. See definition p. 25) and com¬ 
monly abbreviated as “D. C.,” acts or flows continuously in 
one direction. It is commonly considered as flowing from 
positive to negative. In theory the electric impulse, commonly 
referred to as “current flow,” is outward from the positive 
brush of the generator, or positive pole of the battery, on 
one wire of the circuit, along that wire (positive wire because 
it is attached to the positive brush or pole) to and through 
the various lamps, motors, et cetera to the negative wire 
(negative because it is attached to the negative brush or 
pole of the generator) and along that wire back to the nega¬ 
tive pole of the dynamo or battery. 

Alternating current, commonly referred to by the abbrevia¬ 
tion “A. C.,” is the current normally generated in the dynamo 
armature sent out on the circuit without commutation, so that 
the current on the entire system reverses its direction exactly 
the same as it does in the dynamo armature. 

WHY A. C. IS USED.— Knowing that D. C. is best for pro¬ 
jection, and equally good or even better for incandescent 
lighting, and that it may be used for power purposes, the 
novice very naturally inquires why it is not used exclusively. 

There are several reasons why A. C. is used, three of which 
are as follows: First, it is not deemed practical to commu¬ 
tate the current from the armature of a dynamo the voltage 
of which exceeds 500, because of the difficulty of insulating 
the commutator bars. 


14 


HANDBOOK OF PROJECTION FOR 


The second reason is that since wattage, which is the meas¬ 
ure of electrical power, is the product of volts multiplied by 
amperes, the size of a wire necessary to convey a given 
number of horsepower will be much less at high voltage, thus: 
Suppose we wish to transmit 10,000 watts (746 watts equal one 
horsepower) at 100 volts. Since volts times amperes equals 
watts, it follows that watts divided by volts equals amperes; 
hence, to transmit 10,000 watts at 100 volts would require 
10,000-^-100=100 amperes, and the power transmitted would be 
about 13.5 horsepower. But if the voltage were 1,000 instead 
of 100, then only 10,000-H ,000=10 amperes would be required 
to convey the required 10,000 watts of power. 

To put it another way, 100 amperes at 100 volts represents 
exactly the same wattage (horsepower) as does 10 amperes at 
1,000 volts. To carry 100 amperes requires a No. 3 wire, 
whereas 10 amperes can be carried by a No. 16 wire; and 
since a No. 3 wire is .22942 and No. 16 wire .050820 of an inch 
in diameter, it is readily seen that with high voltage a given 
wattage (horsepower) can be conveyed on very much smaller 
wires than could be used were a lower voltage employed. See 
Hawkins’ Electrical Guide, No. 4, page 997, for further 
details. 

Third, still another factor entering into the matter is the 
fact that once the current has been generated and commuted 
into D. C., its pressure (voltage) cannot be raised or lowered 
except by the use of expensive machines having moving parts, 
thus requiring more or less constant attention, whereas it is 
quite practicable to attach a very simple device known as a 
“transformer” (See page 544), which has no moving parts 
and therefore requires practically no attention, to A. C. lines 
at any desired point, the action of which will be to raise 
the voltage to any desired pressure which it is commercially 
possible to insulate, or to lower it to any required voltage. 

It therefore follows that A. C. may be generated at relatively 
low voltage, “stepped up” by means of transformers to any 
required pressure, transmitted for long distances over relative¬ 
ly small wires and again “stepped down” to commercial pres¬ 
sures at destination. Or power for commercial purposes may 
be generated at high voltage, which may be “transformed” 
to a voltage to suit any commercial requirement at any desired 
point along the lines. 

There are other reasons why A. C. is more desirable for 
general commercial use than D. C., but those named are 
perhaps the chief ones. 


MANAGERS AND PROJECTIONISTS 


15 


HOW ALTERNATING CURRENT ACTS.— As already ex¬ 
plained, A. C. constantly reverses its action, flowing in one 
direction for a small fraction of a second, and then in the 
opposite direction for an equal period of time. Commercial 
current now in general use in the United States and Canada 
seldom exceeds 60 cycle and is seldom lower than 25 cycle. 
Taking 25 cycle current for example, the current would flow 
in one direction for l/50th of a second and then in the oppo¬ 
site direction for l/50th of a second. Each of these periods is 
called an “alternation,” and the two periods together represent 
what is known as a “cycle.” (See definition of “cycle,” Page 
26.) If the periods of flow were l/120th of a second, then 
the current would be called “60 cycle,” because there would 
be 60 complete cycles (120 alternations) per second of time. 
With a 25-cycle current there are twenty-five complete cycles 
—fifty alternations—per second. 

Electric dynamos may be built to produce almost any de¬ 
sired number of cycles per second (called “current fre¬ 
quency”), but the two standard frequencies used almost 
universally for commercial work are 25 and 60 cycles per 
second. The first named is employed where the current is 
to be converted to D. C., as in the case of street railways, 
and where the current is to be used mostly for power pur¬ 
poses. Sixty cycle current is used almost universally where 
the current is to be used extensively for both lighting and 
power. 

Low frequency current (25 cycle) is objectionable for light¬ 
ing for the following reasons : If a light be produced by very 
low frequency current there will be a perceptible flicker, due 
to the fact that the E. M. F. sinks to zero twice during each 
cycle, with a consequent dimming of the brilliancy of the 
light, but as the frequency becomes more rapid, the eye is 
unable to follow the rapid changes of brilliancy and the light 
appears to be steady. Due to this cause, 25-cycle current 
has a decided flicker, whereas, insofar as concerns the ability 
of the eye to detect it, 60-cycle current has none at all. 

It is well that the projectionist have at least a fair under¬ 
standing of these various matters, because he is placed in 
direct charge of motors and generators of considerable ca¬ 
pacity, and of projection light which may be seriously affected 
by low current frequency. Moreover, in some places and 
under some circumstance, problems allied to projection may 
arise which can only be successfully coped with by the man 


16 HANDBOOK OF PROJECTION FOR 

who has an understanding of the things we have just set 
forth. 

The action of A. C. is usually expressed by diagram, sim¬ 
ilar to that shown in Fig. 4, the meaning of the various 
details of which we will endeavor to make clear. 

It is quite essential that the projectionist learn to “read” 
such diagrams, because in the study of the details of his pro¬ 
fession he will be constantly confronted with them. 

In Fig. 4 the straight, horizontal line represents time, as 
to its length, and zero pressure or voltage, or no voltage at 
all, with relation to the triangles above and below it. Put in 
another way, the horizontal line represents the point at 
which the alternations of the current are completed, and 



the voltage and amperage are at zero. Put in still another 
way, it would represent the point at which the sides of coil 
sides A—B, Fig 1, stand one above the other, hence cutting 
no lines of magnetic force and generating no E. M. F. 

From 0 to 1 this line represents the time consumed by the 
current in making one alternation. Triangle A above the 
line represents the voltage and amperage action during one 
alternation. At the left of the vertical line the figures repre¬ 
sent voltage. 

Consider line B of triangle A. As the armature coil begins 
to cut lines of force, the voltage (and amperage, of course) 




MANAGERS AND PROJECTIONISTS 


17 


begins to rise, but time is required to accomplish this. If 
the current be 60 cycle it will require l/240th of a second to 
reach the maximum pressure of 110 volts. Line B in its 
length represents the gradual rise of voltage. In its slope 
to the right it represents a lapse of time equal to 1/240th of 
a second. It will also require l/240th of a second for the volt¬ 
age to sink to zero again, as the armature coil gradually 
passes to the position where for an infinitesimal fraction of 
time it cuts no lines of magnetic force, which point is repre¬ 
sented by the point where the right hand side of triangle A 
crosses the horizontal line at 1. It therefore follows that 
from 0 to 1 on the horizontal line represents l/120th of a 
second, or one complete alternation—the time the current 
has been flowing in one direction. 

The armature coil now enters the magnetic field from the 
opposite direction, as is explained in the text accompanying 
Figs. 1 and 2, whereupon the current begins to flow in the 
opposite direction and the whole action is repeated, as per 
triangle C below the line O, triangles A and C representing 
one complete cycle in course of which l/60th of a second has 
lapsed, and the voltage and amperage have twice risen to 
maximum and twice dropped back to zero. If the current 
were 25 cycle, then from 0 to 1 would represent the lapse of 
l/50th of a second and from 0 to 2 the lapse of l/25th of a 
second. 

You will therefore see that in reading diagrams of this sort, 
from right to left means time, and the distance of the triangu¬ 
lar or curved lines from the horizontal represents E. M. F., 
or in other words, voltage and amperage. 

When studying diagrams of this character it must be re¬ 
membered that, while the action is almost inconceivably rapid, 
still when plain, single-phase A. C. is under consideration 
twice during each cycle there is absolutely no voltage or am¬ 
perage on or in the lines. 

It is a bit difficult for the mind of the novice to grasp this 
fact, but it nevertheless is quite true. 

“But,” the student inquires, “if there is no voltage or 
amperage, how is it that the light from A. C. is continuous ?” 

The answer is that the light from single-phase A. C. is NOT 
continuous in brilliancy. Light is produced by either heating 
carbon or an incandescent lamp filament to the point of in¬ 
candescence—white hot—and although the brilliancy of the 
carbon or filament fluctuates with each alternation of the 
current, the action is so very rapid that the eye cannot follow 


18 


HANDBOOK OF PROJECTION FOR 


or even detect it, except in the case of very low cycle current. 
The brilliancy of the light from 60-cycle current is not con¬ 
tinuous, but to the eye it appears to be so because the eye 
functions too slowly to perceive action of such tremendous 
rapidity. 

SINGLE, TWO AND THREE-PHASE A. C.— Alternating 

current may be single-phase, two-phase or three-phase. 
Suppose we have two generators producing precisely the same 
frequency (same number of cycles per second), and that their 
armatures are coupled together by means of a chain belt in 
such way that when the current flow of one is at zero the 
voltage of the other is at maximum. As a result we would 
have “two-phase” current. The voltage of such a circuit is 
never at zero, because when the voltage of one generator is 
at zero in the course of the alternations, the voltage of the 
other is at maximum. The action of two-phase current is 
represented by diagram A, Fig. 5. 


A 




Figure 5. 


If we then couple a third generator to the other two, in 
such manner that the rise and fall of voltage caused by cur¬ 
rent alternations, as is shown in diagram B, Fig. 5, we shall 
have “three-phase” current. 

Two-phase current ordinarily is transmitted by two entirely 
separate circuits of two wires each. Its advantage lies in the 
fact that whereas single-phase current acts intermittently on 
the armature of a motor, much as does the piston of a single 
engine on its load, two-phase acts the same as does a double 
engine, giving a steady pull to the motor armature. 

Three-phase current requires only three wires for its dis¬ 
tribution. It is the ideal system for transmitting electric 
energy through any distance for power purposes. It gives 
a practically steady pull on motor armatures. 

For study of these matters in greater detail, we would 
recommend Hawkins’ Electrical Guide No. 4, page 997 to 
1 , 028 . 


MANAGERS AND PROJECTIONISTS 


19 


Definitions 

I T is desirable that the projectionist know the meaning 
of certain terms used in connection with his work, hence 
we append a somewhat extended list of definitions, making 
no pretense that it. is complete. It is merely designed to 
define those terms with which the projectionist is likely to 
come more or less frequently into contact. Hawkins’ Elec¬ 
trical Dictionary of electrical terms contains more than 500 
pages of definitions. It is an excellent work for such as 
have need for so complete a list. 

ABSORPTION OF LIGHT. —The retaining or absorption 
by a substance, as a lens, of a portion of the light falling 
upon its surface or passing through it. The energy of the 
light thus retained ordinarily is transformed into heat, though 
in some instances its energy is partly absorbed in the work¬ 
ing of chemical change. The absorption by good quality 
glass is about one per cent per inch of distance traversed by 
the light. 

ACETONE. —A liquid obtained as a by-product in the dis¬ 
tillation of wood alcohol. It forms the base of some film 
cement formulas. 

ACTINIC RAY. —A ray of light, or of invisible radiant en¬ 
ergy which can induce chemical action. The violet and ultra 
violet rays are the most powerfully actinic of any of the 
entire spectrum. 

ADHESIVE TAPE. —See insulating tape. 

A. H. —An abbreviation for ampere hour. 

AIR GAP. —Electrically it means a gap or opening in an 
electric circuit which is occupied by air only, as the gap in 
a gas engine spark plug. 

ALIVE. —A term used to describe the condition of a wire 
or other thing .when charged with E. M. F. 

AMMETER. —An instrument for measuring current flow, in 
amperes,. It is also known as the “Ampere Meter.” It is 
the commercial form of the galvanometer. 

AMP. —The most commonly used abbreviation for ampere. 
AMPERE. —The unit of electrical current flow. See page 
51 . 


20 HANDBOOK OF PROJECTION FOR 

AMPERAGE. —The strength of current flow measured in 
amperes. 

AMPERE-HOUR. —One may draw a certain quantity of 
water, say a gallon, from a hydrant in one minute or in ten 
minutes, but regardless of the time consumed in drawing the 
water, it is still one gallon, no more and no less. The same 
holds true in dealing with electric current. A certain given 
quantity may be used in one minute, or in ten minutes. The 
current flowing in any circuit is the relation of the quantity 
flowing to the time during which it flows. If one ampere of 
current flows for a period of one hour, then one ampere hour 
of energy has been consumed; also a flow of two amperes for 
one half hour would be one ampere hour, as would also a flow 
of four amperes for a period of fifteen minutes, or a flow of 
ampere for a period of two hours. Amperes x hours= 
ampere hours. 

AMPERE TURN. —A unit of magneto-motive force equal 
to the force resulting from the effect of one ampere passing 
around a single coil of wire. 

ANGLE OF INCIDENCE.— See page 222. 

ANGLE OF PROJECTION. —The angle the axis of projec¬ 
tion (which see) maKes with a horizontal line level with the 
center of the screen. 

ANGLE OF REFRACTION.— See page 222. 

ANODE. —As applies to projection, the side electrodes of the 
mercury arc rectifier tube. 

APERTURE, PROJECTOR. —The opening in the aperture 
plate of a motion picture projector, the edges of which mask 
the film photograph and give the projected image its outline 
upon the screen. 

APERTURE, PROJECTOR, STANDARD SIZE.— The size 
of the standard aperture is .906 of an inch wide by .6795 of an 
inch high, which is equivalent to 29/32 and 87/128 of an inch, 
respectively. 

ARC.—In lighting, an arc is the result of maintaining an 
E. M. F. between carbons which are somewhat separated, but 
between which current flows across an “arc stream” composed 
of the gases generated in the process of volatilization of car¬ 
bon. The, resultant brilliancy comes mostly from the incan¬ 
descent carbon tips, though the arc stream has some luminosity 
by reason of the fact that it carries particles of incandescent 
carbon. 

ARC VOLTAGE DROP. —The drop in voltage between the 
tips of the carbons of an arc lamp, due to overcoming the 


MANAGERS AND PROJECTIONISTS 


21 


resistance the current encounters in passing from one carbon 
tip to the other. 

ARMATURE. —In a dynamo or motor a core of metal 
mounted on a shaft, around or upon which is a winding of 
wire, the whole being designed to rotate in a magnetic field, 
cut lines of magnetic force and thus produce electric 
energy, or power. 

ARMATURE COIL. —That portion of the winding of an 
armature which would be traced in following an armature 
winding from one commutator segment to the next. 

AUTOMATIC FIRE SHUTTER.— The shutter covering the 
aperture of a projector when it is at rest, the same being 
raised and held open by the action of a governor, when the 
projection speed is such that danger of igniting the film is 
eliminated. 

A. W. G. —The abbreviation of “American Wire Gauge,” 
which is also and commonly known as the “Brown & Sharpe” 
wire gauge. It is the standard in the United States and 
Canada. It measures wires from No. 40 (diameter .00314 of 
an inch) to 0000 (diameter .46 of an inch). 

AXIS OF PROJECTION. —A straight line from center of 
film photograph to center of the image on the screen. 

BACK END .OF ARMATURE. —End opposite from com¬ 
mutator. 

BACK FOCUS. —The distance from film to first surface of 
a projection lens when the picture is in focus on the screen 
and the illuminant sufficiently distant to illuminate the film 
with parallel rays of light, as in the case of a film illuminated 
by the sun. A condition never, of course, met in actual 
practice. See “Working Distance.” 

BALANCED ARMATURE. —One which will run without 
vibration. 

BALANCED LOAD. —A load carried by two generators, 
as in the 3-wire system, is said to be “balanced” when each 
generator carries an equal load, or when the load is equal 
on both “sides” of the system. 

BEAM OF LIGHT.— A bundle of light rays. A pencil or 
line of light of greater area of cross section than a single 
ray. 

BLOWING A FUSE.— The melting of a fuse, usually due to 
overload, though it may be caused by mechanical heat gen¬ 
erated by poor electrical contact of the fuse with its contacts. 


22 


HANDBOOK OF PROJECTION FOR 


BLOWING POINT— The number of amperes (flow of cur¬ 
rent) necessary to blow a given fuse is the “blowing point” 
of that fuse. 

BRUSH. —A device for making electrical contact between 
the rotating commutator, or collecting rings of a generator, 
and the stationary circuit wires. Brushes are made from car¬ 
bon, copper wires, copper strips and copper gauze, but car¬ 
bon brushes are most largely used. 

BRUSH LOSS. —Loss, in watts, due to lack of perfect elec¬ 
trical contact between brush and commutator or collector ring. 
May be greatly increased by dirty brushes, dirty, rough 
commutator or lack of sufficient pressure between brushes 
and commutator. 

BRUSH ROCKER. —The rocker or yoke to which dynamo 
and motor brush holders are attached. Its purpose is to per¬ 
mit the shifting of the brushes around the commutator to 
the neutral point. 

BUS BARS. —Name commonly applied to the heavy copper 
bars used on switchboards where a large number of circuits 
are to be served. Strictly speaking, this name may only be 
properly applied to power house heavy copper bars connecting 
with the generators. 

BUZZER. —An electric signal which makes a buzzing sound. 

B. X. —A flexible metal tubing for the protection of electric 
wires, much used for interior work. A flexible metal conduit. 

CABLE.— A single copper wire, or strand of such wires, 
heavily insulated and covered with a metal sheath, usually of 
a lead composition. 

CALCIUM LIGHT. —An intense white light produced by 0 the 
incandescence of a spot on a pencil of lime when a mixture 
of oxygen and hydrogen gases is burned in contact there¬ 
with. Also called “lime light.” Used for projection where 
electric current is not available, but is a very unsatisfactory 
illuminant for motion picture projection as compared with 
electric light. 

CALIPERS.— Instruments with which to measure external 
and internal diameters. 

CAM.— A revolving disc fixed to a shaft and designed to 
impart to a second element, with which it is in constant or 
intermittent contact, a variable velocity or motion, or an 
intermittent motion. 

CAMERAMAN. —The one who does the actual photograph- 
: ng in the production of motion pictures. 

CANDLE. —The unit of illumination, as one candle power. 


MANAGERS AND PROJECTIONISTS 


23 


CANDLE FOOT OR FOOT CANDLE.— A unit of illumina¬ 
tion, being the light given by a British standard candle at 
one foot distance. It is equal to 10.764 candle meters, which 
see. 

CANDLE METER. —A unit of illumination, being the il¬ 
lumination of a standard candle at the distance of one meter. 

CANDLE, STANDARD. —The standard candle by which 
all lights are measured is legally held to be a sperm candle 
consuming 120 grains of wax per hour. In practice standard¬ 
ized incandescent lamps are more reliable. The standard 
unit of candle power established by the National Bureau of 
Standards at Washington equals 100/80ths of the Hefner unit 
under Reichsanstalt standard condition. 

CARBON ARC. —A voltaic arc occurring between carbon 
points, as in an arc lamp. 

CARBON BRUSHES. —Commutator brushes made from 
carbon, sometimes coated with copper to insure better elec¬ 
trical contact with holders. 

CARBON ELECTRODES. —The carbons used in an arc 
lamp. 

CARBON JAW.— The jaw of an arc lamp by means of 
which the carbons are gripped and held. 

CARBONS. —The carbon rods or pencils used in an arc 
lamp. 

CARRYING CAPACITY— Greatest number of amperes an 
electrical conductor can safely carry. 

CARTRIDGE FUSE.— See page 109. 

CATHODE.— In projection the lower, mercury, contact of a 
mercury arc rectifier tube or bulb. 

CELLULOID.— A hard, flexible substance formed by dis¬ 
solving camphor in alcohol and adding pyroxylin. The re¬ 
sultant mass is incorporated between rollers. 

CEMENT, FILM— A cement, or chemical solvent, by means 
of which two pieces of film may be joined or spliced together. 
All film cements are volatile, therefore must be kept tightly 
corked when not in use. 

CEMENT LINED CONDUIT— Conduit having its interior 

surface coated with cement. 

CENTER LENS. —The lens between the collecting and con¬ 
verging lenses in a 3-lens condenser combination. 

CHANGE-OVER.— In projection, the act of changing from 
one projector to another without interrupting the continuity 
of action upon the screen. 


24 


HANDBOOK OF PROJECTION FOR 


CHATTERING BRUSH.— The rattling of a brush on the 
face of a commutator, usually caused by the same being loose 
in holder. 

CHOKING COIL. —(Commonly called “choke coil”). A coil 
of wire wound on an iron core so as to give self-inductance 
with small resistance, used on A. C. to impede the current 
with slight loss in power, also called an “impedance coil” or 
“reactance coil.” « 

CHROMATIC ABERRATION.— See page 130. 

CIRCUIT BREAKER. —A device, somewhat similar to a 
switch, by means of which a dangerous variation in current 
flow will operate electro magnets and open the circuit. Cir¬ 
cuit breakers are made to operate both for over- and under¬ 
load. 

CIRCULAR MEASURE. —Every circle is divided into 360 
equal parts, called degrees. A degree is 1 /360th the circum¬ 
ference of a circle, regardless of the diameter of the circle, 
hence a degree has no set dimension as to its width or length, 
but increases in width or length with every increase of circle 
diameter. Each degree is subdivided into 60 minutes, and 
each minute into 60 seconds. 

CIRCULAR MILL.— The area of a circle, 1/1000th of an 
inch in diameter. The square of the diameter (multiplying 
diameter by itself) of any circle, in mills (thousandths of an 
inch) gives its area in C. M. 

C. M. —Abbreviation for circular mill. 

CLOSED CIRCUIT. —A circuit in which continuous contact 
permits a constant flow of current. 

COLLECTING RINGS. —Rings of A. C. generator upon 
which the brushes rest, and from which the current passes 
into the brushes and thence to the outside circuit. 

COLLECTOR LENS. —The lens of the condenser combina¬ 
tion which is next the light source. 

COMBINATION PROJECTOR. —A motion picture projec¬ 
tor equipped with a stereopticon attachment. 

COMMUTATOR. —An arrangement of copper commutator 
bars by means of which the alternating current of the arma¬ 
ture is changed to direct current in the outside circuit. 

COMPOUND WINDING. —A method of winding a dynamo 
or motor field magnet with two sets of coils, one of which 
forms a shunt circuit, the other carrying the entire output of 
the armature, except what flows through the shunt circuit. 


MANAGERS AND PROJECTIONISTS 


25 


CONDENSER. —In projection, a combination of lenses de¬ 
signed to collect the diverging rays from the light source, 
and to refract.and converge them upon the projector aperture. 

CONDUCTOR. —(a) Any substance which will transmit elec¬ 
tric current, though the name is ordinarily only applied to 
those having low resistance, (b) A wire or a copper bar 
used to transmit electrical energy. 

CONDUIT. —A metal or armored tubing in which electric 
wires are placed for their protection. 

CONJUGATE. —United in pairs; yoked together; coupled. 

CONJUGATE FOCI.— See page 127. 

CONNECTOR. —A device for joining wires electrically in 
such manner that they may be readily released. 

CONSTANT CURRENT DYNAMO.— A dynamo so wound 
that it will deliver constant amperage under varying load. 
Such a generator varies its voltage instead of its amperage. 

CONTINUOUS CURRENT. —A non-pulsating current which 
is constant both as to pressure and direction of flow. See 
Direct Current. 

CONVERGING LENS. —The lens of a condenser combination 
which is farthest away from the light source. 

COPPER. —Next to silver the best metallic conductor of 
electricity and of heat known. 

COPPER LOSS. —The loss of energy resulting from re¬ 
sistance offered to the flow of current through a copper 
wire. See Voltage Drop. 

CORED CARBONS. —Projection carbons having a core 
composed of ground, baked carbon, mixed with a suitable 
binder, usually water glass. 

COVER GLASS. —The glass which covers the photograph 
on a stereopticon slide. 

C. P. —The abbreviation for candle power. 

CRATER OF ARC. —The concave depression produced on 
the tip of the positive carbon of arc lamps by action of the 
current. 

CRATER ANGLE. —The angle at which the crater is with 
relation to the axis of the optical train. The most efficient 
angle is 55 degrees. 

CRATER PROJECTOR.— A means for projecting an image 
of the crater. It may be a pin hole in the lamp house door 
in conjunction with a lens, or merely a pin hole, or a pin 
hole, a lens and a reflector to direct the image to any desired 
spot. 


26 


HANDBOOK OF PROJECTION FOR 


CRITICAL ANGLE. —The angle of incidence beyond which 
rays of light are no longer refracted into a transparent 
medium, but are reflected from its surface. . 

CYCLE. —A series of operations. As applied to A. C., the 
cycle is two complete alternations. 

DIMMER. —An adjustable resistance inserted in an incan¬ 
descent circuit by the manipulation of which the lights of the 
circuit may be gradually dimmed or brightened. 

DIOPTER. —The unit for expressing the refractive power 
of a lens. It is the power of a lens whose focal length is one 
meter. 

DIRECT CURRENT (D. C.).— A current constant in direc¬ 
tion, though not necessarily in value. A direct current con¬ 
stant both in direction and value is called a continuous cur¬ 
rent. Direct Current, which, while continuous in direction, 
pulsates as to pressure, is often wrongly called continuous 
current. 

DIRECT CURRENT CONVERTER.— A machine for con¬ 
verting D. C. of one voltage to D. C. of a different voltage. 

DISSOLVE. —The gradual transition or fading of one pro¬ 
jected image into another. 

DIVERGING BEAM. —A light beam which diverges away 
from its immediate source. 

DOUBLE THROW SWITCH.— A knife switch which may 
be thrown over into either of two sets of contacts. 

D. P. SWITCH. —Abbreviation for double pole switch. 

DEGREE. —A unit of measurement of temperature. 

DEGREE. —The circumference of every circle is divided 
into 360 equal parts called degrees, hence a degree is l/360th 
part of the distance around the circumference of any circle. 
It is, therefore, evident that with every increase or decrease 
in circle diameter the linear measurement of a degree changes, 
insofar as applies to that particular circle. Each degree 
is divided into sixty equal parts, called minutes, and each 
minute is divided into sixty seconds. 

DENSITY OF FIELD. —The quantity of electromagnetic 
lines of force existing in a unit of cross section area of an 
electro-magnetic field. 

DETERIORATION OF INCANDESCENT LAMP.— The de¬ 
crease in candle power of an incandescent lamp which takes 
place after prolonged use. 

DIFFERENTIAL WINDING OF FIELD.— A method of 

winding a field magnet with double coils in such a way that 
each exerts a pull against the other. 


MANAGERS AND PROJECTIONISTS 


27 


DIFFUSION.— As applied to light, its reflection by a sur¬ 
face in such a way that it is scattered. See page 222. 

DIRECT COUPLED DYNAMO. —One having its armature 
shaft coupled direct to the shaft of the source of power 
which drives it. 

DIRECT CURRENT DYNAMO.— A dynamo supplying di¬ 
rect current, which may or may not be continuous current. 

DIRECTOR. —One who directs the actors during the mak¬ 
ing of a scene or scenes of an entire production. 

DOUBLE POLE SWITCH. —A switch which controls both 
wires of a two-wire circuit,- as a two-blade knife switch. 

DOUBLE THROW SWITCH. —A knife switch which may 
be thrown over into either of two sets of contacts, thus con¬ 
necting its center contacts to either of two entirely different 
circuits. 

DOUSER. —A manually operated shutter in the lamphouse 
or in the condenser cone by means of which the light may 
be intercepted before reaching the spot, or, in the case of a 
stereopticon, the lens. 

D. P. SWITCH. —An abbreviation, meaning double pole 
switch. 

DROP IN POTENTIAL. —A drop in voltage due to resist¬ 
ance of the lines. May be due to length of lines or to over¬ 
load. 

DRY CELL. —A battery or primary cell usually made up 
of a jar composed of zinc, which forms one of the elements 
or electrodes. The other element is of carbon, suspended 
so that it cannot come into contact with the zinc. The re¬ 
maining space is filled with an absorbent substance saturated 
with sal ammoniac. 

E. E. —Abbreviation for Electrical Engineer, a degree con¬ 
ferred upon students by technical schools when they have 
completed a course in electrical engineering. 

EFFICIENCY. —As applied to motors, generators and trans¬ 
formers, the ratio of power applied at the input terminals to 
the power available at the output terminals. It is found by 
dividing the watts output by the watts input, thus: If the 
input of a motor be 10 amperes at 110 volts, or (100 x 10) 
1100 watts, and the output be 900 watts, the efficiency of the 
motor would be 900 1100 = 81 -f- per cent. 

ELECTRODES. —In arc lighting, the carbons which form 
the terminals of the lamp. 

ELECTRO MOTIVE FORCE.— That force which creates and 
maintains an electric current in, on or through a conductor. 


28 


HANDBOOK OF PROJECTION FOR 


It is commonly termed voltage. It is measured in volts. It 
is abbreviated E. M. F. 

EQUIVALENT FOCUS.— See page 129. 

EXCHANGE. —A central repository from which film may 
be had, usually on a rental basis. 

EXHAUST FAN— A fan used to pull .or pump air out of 
a room, or other inclosure; a fan designed to create a 
vacuum. 

F. —Abbreviation for Fahrenheit. On its scale 32° repre¬ 
sents the melting point of ice and 212 the boiling point of water 
at sea level. 

FADE-IN. —The gradual appearance of the picture from 
darkness to full brilliancy, 

FADE-OUT. —Opposite from fade-in, which seg. 

FEATURE. —A photoplay to be used as the leading part of 
a theatre bill or program. 

FIELD MAGNETIC. —The space occupied by magnetic lines 
of force. 

FIELD COILS. —The coils of wire wound on the field mag¬ 
nets of a dynamo. 

FIELD MAGNETS. —In a dynamo or motor the magnets 
forming the magnetic field in which the armature revolves. 

FIELD POLES. —The poles of the magnets in the field of 
which the armature revolves. 

FIELD RHEOSTAT. —An adjustable resistance used to con¬ 
trol the amount of current flowing in the field coils of a dyna¬ 
mo or motor, hence an adjustable resistance by means of 
which the strength of the magnetic field is varied. 

FILM. —In projection, a ribbon of celluloid upon which the 
photographs constituting a motion picture are carried. 

FILM CEMENT.— See Cement. 

FILM MENDER OR SPLICER. —A device used to correctly 
join the sprocket holes and clamp the ends of the film to¬ 
gether when splicing film. 

FIXED RESISTANCE. —A resistance having a given, fixed 
value, as a non-adjustable rheostat. 

FLAMING OF ARC. —In projection a flame emanating from 
the tips of the electrodes of an electric arc under certain con¬ 
ditions. Its cause may be any one of several things, includ¬ 
ing impure carbon, carbons working above capacity, high am¬ 
perage and a too great distance between carbon tips. 

FLAT COMMUTATOR SEGMENT.— A commutator seg¬ 
ment which has become flat through wear, burning or faulty 
adjustment. 


MANAGERS AND PROJECTIONISTS 


29 


FLATS. —Spots on commutator which have become flat, or 
slightly depressed through wear, or from other cause. 

FLOATING BATTERY. —A storage battery so connected to 
a parallel system that it will be charged by it or to automat¬ 
ically discharge into it, as required. 

FOCUS. —The point of concentration. The point at which 
light rays meet and form an image after being subjected to 
the action of a lens. 

FOCUSING SCREW. —Thumbscrew by means of which the 
projection lens is moved forward or backward to focus the 
image on the screen. 

FOOT CANDLE. —A unit of illumination; the light of a 
standard candle at a distance of one foot. 

FOOTAGE. —Film length measured in feet. 

FRAME (noun). —A single photograph on a motion picture 
film. 

FRAME (verb). —To so adjust the projector framing device 
that the film photograph is in correct register over the 
aperture. 

FRAME LINE. —The line between the top of one image and 
the bottom of the next in a motion picture film. 

FREQUENCY.— The number of double alternations per 
second, commonly referred to as “cycles.” 

FRICTIONAL LOSS. —In any machine the amount of energy 
expended in overcoming the resistance caused by the fric¬ 
tion of its various parts. 

FRONT END OF ARMATURE. —The commutator end. 

FRONT WALL. —As applied to the projection room, the 
wall next the screen. As applied to the auditorium, the wall 
at the stage or screen end. 

FUSE.— See page 107. 

FUSE ALLOY.— See page 107. 

FUSE BLOCK. —A slab or “block” of insulating material 
carrying one or more fuses. 

FUSE LINKS, OR LINK FUSES.— See page 111. 

GAS STREAM.— The stream of gas between the carbon 
tips of an arc lamp. It is formed by the volatilization of 
carbon and has considerable conductivity as compared with 
the surrounding air. 

GENERATOR. —Same as dynamo, which see. 

GERMAN SILVER.— A metal alloy composed of copper, 
zinc, and nickel in varying proportions. Much used for re¬ 
sistance wire where a uniform resistance at varying tempera¬ 
tures is important. 


30 


HANDBOOK OF PROJECTION FOR 


GLASS.— A substance made by melting together sand or 
silica with lime, potash, soda or lead oxide. By varying the 
proportions of these ingredients different kinds of glass are 
obtained, such as bottle, plate, flint, crown, etc. 

GRAPHITE— One of three forms in which carbon occurs 
in nature. Also called plumbago. Useful.to the projectionist 
as a lubricant for the arc lamp, since it is an excellent lubri¬ 
cant and is but little affected by high temperature. 

GRID. —As applied to projection, one resistance of a grid 
rheostat. See figure 132, page 416. 

GROUND. —(a) Broadly it is a term used to designate a 
current carrying connection of such high resistance that it 
is not a short circuit, but which nevertheless enables the 
current to reach opposite polarity without traveling its 
allotted path, (b) An electrical contact of one or both polar¬ 
ities with earth, (c) An electric contact of one polarity with 
something it is not intended shall be electrified. 

GROUND WIRE. —In projection a wire connecting a pro¬ 
jector frame with earth. 

HARD SOLDER. —A solder which melts at red heat only. 
May be made from zinc and copper. 

HIGH COMMUTATOR BAR. —A condition where one or 
more bars or segments of a commutator are higher than the 
others. Unless remedied it will work very serious harm to 
the commutator. 

HORIZONTAL CANDLE POWER. —Illuminating power of 
a light source in a horizontal direction. 

HORSE POWER. —One horse-power (h.p.) equals 33,000 
foot-pounds of work per minute. It is the theoretical amount 
of work one strong draft horse is supposed to perform if a 
block and tackle be attached to a weight of 33,000 pounds and 
the tackle be of such proportion that the horse can, by exert¬ 
ing his full strength, just raise the 33,000 pounds one foot 
while walking outward pulling on the rope for a period of 
one minute. Under these conditions one horse-power has 
been exerted during that minute. That is the theory of the 
thing. One horse-power-hour is the amount of work exerted 
by one horse during one hour, or by 60 horses during one 
minute, or by 3600 horses during one second. In electrics 746 
watts is supposed to represent the raising of 33,000 pounds 
one foot in one minute, or, in other words, one horse power. 
The unit was established as follows : 1 watt is equivalent to 
1 joule per second (the joule is the practical C. G. S. unit of 
electrical energy. One joule is equal to .73734 of a foot- 


MANAGERS AND PROJECTIONISTS 


31 


pound, or, .00134 h.p.-seconds; it is the quantity of electric 
energy necessary to raise the potential of one coulomb of elec¬ 
tricity one volt in pressure) or 60 joules per minute, and 1 
joule is equal to .73734 of a foot-pound, therefore 60 joules = 
60 x .73734 = 44.24 foot-pounds. Now, since one horse-power 
equals 33,000 foot-pounds per minute the electrical equivalent 
would be 33,000 44.24 = 746 watts. 

HOUSE SERVICE WIRES.—The wires connecting the main 
house cutout with the street mains or transformer. 

IMAGE.—In projection optics an image is an image or pic¬ 
ture of an object (transparent photograph on film or slide) 
formed on a receiving surface called a screen, by light rays 
focused by a lens. 

INCLOSED SWITCH.—A knife switch inclosed in a metal 
housing for the protection of its live parts. 

INDUCTION.—The influence which a mass of iron charged 
with A. C. exercises upon surrounding bodies of metal, without 
having any actual metallic connection therewith. 

INSULATION.—The employment of substances having high 
resistance to confine electric current to the conductor, and 
prevent it escaping to a conductor of opposite polarity. Rub¬ 
ber, porcelain and glass are examples of high resistance 
insulating materials. 

INSULATING TAPE.—A cloth tape impregnated with an 
insulating compound, usually composed of coal tar and resin 
in proportions of about 30 to 40. The compound causes it to 
be adhesive. It is used to insulate wire splices, etc. 

INTERMITTENT MOVEMENT.—The mechanism by 
means of which the intermittent sprocket is operated. 

INTERMITTENT SPROCKET.—The sprocket of a pro¬ 
jector by means of which the film is given its intermittent 
movement at the aperture. 

KILOGRAM.—A unit of mass in the metric system. It 
equals 2.2064 pounds. 

KILOMETER.—1,000 meters; 3,280.899 feet; or .62138th of a 
mile. 

KILOWATT.—One thousand watts, which equals 1.34 horse¬ 
power. 

KILOWATT HOUR.—The use of one kilowatt of electric 
energy for one hour. 

KNIFE SWITCH—A switch having a movable blade or 
blades, usually of copper, which are hinged at one end and 
make or break contact with parallel spring contact clips at 


32 


HANDBOOK OF PROJECTION FOR 


the other. The switch blade takes the place of the con¬ 
ductor between its contact points. 

K. W.—Abbreviation for kilowatt. 

K. W. H.—Abbreviation for kilowatt hour. 

LAMP ANGLE.—The angle at which the projector lamp, as 
a whole, sets with relation to the axis of the projector optical 
train. 

LAMPHOUSE.—The metal housing surrounding the light 
source and carrying mount for the condenser lenses. 

LAMPHOUSE VENT PIPE.—The pipe leading from the 
lamphouse to the open air, or to some flue connecting there¬ 
with, by means of which the heat and gases generated inside 
the lamphouse are removed from the projection room. 

LEADER.—A short length of film attached to the leading 
title of a subject, or to the beginning of a reel of film, in order 
to protect it and to allow of threading into the take-up with¬ 
out using the film title for the purpose. 

LENS.—(a) A transparent medium, usually glass, having one 
or more curved surfaces, for the purpose of changing the 
direction of rays of light, giving them a direction largely 
determined by the curvature of the lens surface or surfaces, 
(b) A combination of single lenses mounted together so as 
to act as a single (compound) lens. 

LENS JACKET.—The outer part of a projection lens, which 
usually carries the focusing mechanism and holds the inner 
lens tube in which the lenses are mounted. 

LENS PORT.—The opening in the front wall of .the pro¬ 
jection room through which the beam from the projection lens 
passes. 

LENS, PROJECTION.—See “Projection Lens.” 

LIGHT BEAM.—See “Beam of Light.” 

LIGHT RAY.—A thin line of light having no appreciable 
area of cross section. 

LOOP.—In projection, the slack film left between the upper 
sprocket and the top of the gate tension shoes, and between 
the lower end of the gate tension shoes and the lower sprocket, 
in order that the film between the two loops may stop and 
start intermittently while the rest of the film has continuous 
motion. 

MAGNET.—In the ordinary acceptance of the term, a body 
of iron charged wtih magnetism and generating a magnetic 
circuit or field. A magnet may be a permanent magnet (a 
polarized electro-magnet), in which case the magnetic field 
is always present in considerable strength, or it may be an 


MANAGERS AND PROJECTIONISTS 33 

electromagnet only when “excited” by passing a current of 
electricity over wires wound around it. Magnets, either perma¬ 
nent or otherwise, may be made more powerful by passing 
an electric current over wires coiled around them. 

MAGNET COIL.—A coil of insulated wire wound around an 
electro-magnet, over which current is passed in order to in¬ 
crease the density of the magnetic field produced by the 
magnet. Also called “Field Coils.” 

MAGNET CORE.—The bar of iron or steel around which 
the magnet coil is wound. 

MAGNETIC DENSITY.—The number of lines of magnetic 
force passing through a magnetic field per unit of cross sec¬ 
tion area. 

MAGNETIC FIELD.—(a) The space immediately surround¬ 
ing the poles of a magnet through which the magnetic force 
acts. It is strongest near the surface of the magnet poles, 
decreasing rapidly in strength with distance, finally disappear¬ 
ing entirely, (b) The space immediately surrounding any 
wire conveying alternating current. 

MAGNETIC FLUX.—The average intensity of a magnetic 
field multiplied by its area. The total strength of a magnetic 
field. 

MAINS.—A term variously used, but commonly designating 
the wires of the principal distribution circuits of an electric 
system. 

MAINS, STREET.—The wires of the street circuit which 
supplies the house service wires. 

MAT.—In projection, the paper mask used to outline the 
photograph of a stereo slide. 

MEAN SPHERICAL CANDLE POWER.—The average 
spherical candle power. 

MELTING POINT.—The temperature at which substances 
begin to melt or fuse. An alloy consisting of one part tin 
and one part lead, melts at from 375 to 460 degrees. Tin melts 
at from 442 to 446 degrees. 

Lead melts at from. 608 to 618 degrees 

Silver melts at from. 1733 to 1873 

Copper melts at from. 1929 to 1996 

Steel melts at from. 2372 to 2532 

Wrought Iron melts at from. 2732 to 2912 

MENISCUS.—A lens which is convex cn one surface and 
concave on the other. 

METER.—The unit of length in the metric system. Equals 
39.37 inches. 







34 


HANDBOOK OF PROJECTION FOR 


METER.—An instrument for measuring. 

MICA.—A mineral substance, mined in certain places. It 
is semi-transparent, may be split into very thin sheets and 
has high insulating and heat resisting powers. It is used for 
projection arc lamp insulation. 

MIL.—A unit of length. l/1000th of an inch. 

MIL-FOOT.—A wire one mil in diameter and one foot in 
length. 

MIL-FOOT STANDARD.—The standard of resistance in 
wires. See page 73. 

MISFRAME.—In a film a wrongly made splice through which 
a part of one photograph is eliminated. In projection the 
showing of a portion of two pictures on the screen at the 
same time. 

MOTOR, ELECTRIC.—A machine for transposing electrical 
power into mechanical power. 

MOTOR GENERATOR.—In projection, a machine consist¬ 
ing usually of an A. C. motor direct connected to a D. C. 
generator for the purpose of generating D. C. with power, 
supplied by A. C. The resultant D. C. may be of higher, lower, 
or the same voltage as the A. C. supply, but for projection 
work it is, in modern and efficient machines, supplied at arc 
voltage by a generator wound for constant current. Also 
see “Rotary Converter.” Motor generators are also used in 
projection for the purpose of reducing D. C. supply to pro¬ 
jection arc voltage. 

MOTOR GENERATOR SET.—See “Motor Generator.” 

MULTI-PHASE.—A term applied to any A. C. system hav¬ 
ing more than one phase. Polyphase is the term more com¬ 
monly employed. 


MULTIPLE REEL.—A photoplay several reels in length. 


NAILS.—Nails 
will be useful: 

are used everywhere. 

The following table 

Size 

Length 

No. of Nails to Lb. 

3 penny 

1-inch 

557 

4 penny 

154 -inch 

353 

5 penny 

1 2/3-inch 

232 

6 penny 

2-inch 

167 

8 penny 

254-inch 

101 

10 penny 

2j4-inch 

88 

12 penny 

3-inch 

54 

18 penny 

354-inch 

44 

20 penny 

354-inch 

34 

Spikes 

4-inch 

16 


MANAGERS AND PROJECTIONISTS 


35 


NATIONAL ELECTRIC CODE.—A national code of rules 
based on the requirements of the fire underwriters. The 
requirements of the code must be observed as to inside elec¬ 
tric wiring and other work in order to get insurance on a 
building. Copies of the code may be had by applying to the 
National Board of Fire Underwriters, Electrical Department, 
Room 1100, No. 123 William Street, New York City. It is sent 
free of charge, but we would suggest that you send five cents 
in stamps for postage. It is a 216-page book. 

NEGATIVE.—The opposite to positive. In electrical ap¬ 
paratus the pole toward which the current is presumed to 
flow. 

NEGATIVE CARBON.—In a D. C. arc lamp the lower car¬ 
bon to which the current flows across the arc from the posi¬ 
tive carbon. 

NEGATIVE FILM.—The film which is exposed to light in 
the camera. The film upon which the original image is im¬ 
pressed. The film from which positive prints are made. 

NEGATIVE POLE.—Opposite pole to positive. In a dynamo 
or battery the pole to which the current is presumed to return 
from the external circuit. 

NEGATIVE WIRE.—A wire attached to the negative pole. 
A wire having negative potential. 

NEUTRAL WIRE.—In a 3-wire system the center wire or 
conductor is the “neutral.* It is negative to one outside wire 
and positive to the other, when either side is used separately. 

NEUTRAL WIRE AMMETER.—An ammeter connected 
into the neutral wire to determine how nearly the load is in 
balance. It may be attached to any circuit or to the service 
wires of any building, if desired. The amount it records is 
the' amount the load is out of balance. 

NICKEL STEEL.—Ordinary soft steel to which a small per¬ 
centage of nickel has been added. Best results are had with 
about 3.25 per cent, of nickel. 

OBSERVATION PORT.—The opening in the front projec¬ 
tion room wall through which the projectionist views the 
screen. 

OHM.—The unit of resistance. See page 53. 

OHM’S LAW.—The law that, considering a uniform flow of 
current in a given circuit, the amperage is equal to the E. M. 
F., in volts, divided by the resistance in ohms. The law is 
expressed by simple formulas. See page 55. 

OIL WELL.—(a) An oil-tight receptacle in which the inter¬ 
mittent movement of a modern projector is placed so that it 


36 


HANDBOOK OF PROJECTION FOR 


may work in an oil bath, (b) A cavity under a dynamo or 
motor bearing which contains oil for lubrication of the bear¬ 
ing. See “Ring Oiling.” 

OPEN CIRCUIT.—A circuit which is not complete as to 
electrical connection. A circuit which has been broken, as by 
the opening of a switch. 

OPTICAL AXIS.—A line passing through the center of a 
lens which is perpendicular to its plane. In a projector optical 
train a line from the center of the light source to the center 
of the front lens of the projection lens, when all elements are 
in proper adjustment. 

OPTICAL TRAIN.—In a projector, the various lenses it em¬ 
ploys referred to as a whole. 

OUTLET.—A point in ceiling or wall out of which wires 
are led to make connection with lamps, motors, etc. 

OUTLET BOX.—An iron box, usually circular in form, lo¬ 
cated at an outlet to protect the splices and to serve as an 
anchorage for the circuit conduit. 

OUT OF FOCUS.—When the image is not sharp on the 
screen. See page 146. 

OUTPUT.—The electrical energy delivered by a dynamo. 

OUTSIDE TRANSFORMER.—Transformer by means of 
which the service wires of the theatre are fed. Usually re¬ 
ferred to as the pole transformer. 

OUTSIDE WIRING.—Wiring attached to the surface—not 
concealed. 

OVERLOAD.—A load greater than a machine is designed to 
carry. 

OVERLOAD CAPACITY.—The amount of overload an 
electrical device or a machine may carry, either permanently 
or for a stated period, without sustaining permanent injury. 

OVER-SHOOTING.—The carrying of the film too far by 
momentum, due to lack of sufficient tension by the gate ten¬ 
sion springs. Failure of the film over the aperture to stop 
exactly when the intermittent sprocket stops. 

OZONE.—A gas of a faint bluish tint and a characteristic 
odor. It is produced by passing a current of electricity 
through air, changing the oxygen to ozone. It has purifying 
and sterilizing properties. 

PANEL BOARD.—Name applied to a small distributing 
switchboard, usually located in the wall of a room, auditorium 
or hallway, and controlling several circuits, or perhaps all the 
circuits on a single floor. 


MANAGERS AND PROJECTIONISTS 


37 


PANEL BOARD FEEDERS. —Circuit wires attached to the 
panel board bus bars. 

PANEL BOARD FUSES. —Fuses controlling the circuits 
controlled by a panel board. 

'K.PARALLEL CONNECTION (also called Multiple Conner 
tion).—(a) A circuit in which two or more incandescent lamps 
are connected between the two wires of the circuit, (b) The 
connection of the two projection arc lamps in such way that 
both positives are connected to positive and both negatives to 
negative, with but one rheostat for both lamps. Under this 
condition both lamps cannot be burned at one time. When 
the carbons of the idle lamp are brought into contact the 
other arc goes out. (c) As applies to rheostats on a projec¬ 
tion circuit, a connection made in such a way that the wire 
from the supply connects to one terminal of both rheostats 
and the wire leading to the lamp to both of the other rheo¬ 
stat terminals. See page 426. 

PERFORATIONS. —Holes punched in film which engage 
with projector sprocket teeth and give film its movement. 
Commonly called “sprocket holes.” 

PERMANENT GROUND.— See page 346. 

PHASE SPLITTER. —A device for producing two currents 
from single phase current which will differ in phase, the 
purpose being to assist in starting a single phase induction 
motor. 

PHASE SPLITTING. —The process of changing a single 
phase current into polyphase currents. 

PHOSPHOR BRONZE. —An alloy of copper, tin and from 2 
to 5 per cent, of phosphorus. This alloy is superior to pure 
copper in strength, but lacks conductivity as compared to 
copper. It is very durable, and is used for projector wearing 
parts by some manufacturers. 

PLANO. —A term used in connection with lenses. It means 
a flat surface. 

PLANO CONVEX.— A lens which is flat on one side and 
convex on the other. 

PLUMBAGO.— See “Graphite.” 

POLARITY.— See page 3. 

POLARITY SWITCH.— A D. P. D T. knife switch so wired 
that throwing it over reverses the polarity of the wires of 
the circuit it controls. See page 350. 

POLYPHASE CURRENTS.— Same as two and three-phase 
currents, which see, page 18. Any current having more than 
a single phase. 


38 


HANDBOOK OF PROJECTION FOR 


PORT. —In projection, an opening in the front wall of the 
projection room. 

POSITIVE. —As applied to photography, a “print” from a 
negative. The films used in projection are positive prints. 

POSITIVE BRUSHES. —The commutator brushes of a dy¬ 
namo or motor which connect with the positive wire of the 
circuit. 

POSITIVE CARBON. —In a D. C. arc lamp the upper car¬ 
bon; the carbon to which the positive wire of the circuit is 
attached. 

POSITIVE PRINT. —Film exposed to light passing through 
a negative. The film used in projection is a “positive” print. 

POSITIVE POLE. —The positive (+) terminal of a genera¬ 
tor from which the current is assumed to flow out to the exter¬ 
nal circuit. 

POSITIVE WIRE. —The wire connected to the positive 
pole of an electric generator and charged with positive (+) 
E. M. F. 

POWER. —The rate at which work is done, meaning work 
divided by the time in which it is done. The generally ac¬ 
cepted unit is the horsepower, which is 33,000 foot pounds a 
minute. See “Foot Pound.” 

PRIMARY COIL.— In a transformer, a coil consisting of 
many turns of insulated copper wire wound around one “leg” 
of an iron core, or placed within a laminated iron core. In 
effect it is a powerful choke coil, its practical purpose being 
t-o create a magnetic field in order that a secondary current 
may be induced in a secondary coil placed within the mag¬ 
netic field thus created, the voltage of which latter will be 
dependent upon the relative number of turns of wire in the 
two coils. 

PRIMARY CURRENT. —The current in the primary coil of 

a transformer. 

PROJECTION ANGLE.— See page 255. 

PROJECTION DISTANCE. —Distance from projection lens 

to screen. Commonly referred to as “throw.” 

PROJECTION LENS. —The lens combination which forms 
the image upon the screen. The lens of a projector optical 
train corresponding to the objective in a camera. Also termed 
“projection objective.” 

PROJECTION SPEED. —The speed at which the film is pro¬ 
jected, expressed in feet a minute. 


MANAGERS AND PROJECTIONISTS 


39 


PROJECTION SPEED, NORMAL. —Normal speed of pro¬ 
jection as fixed by the Society of Motion Picture Engineers is 
60 feet of film a minute. 

PROJECTION SPEED, PROPER. —The proper projection 
speed is a speed exactly equal to the camera speed at which 
any individual scene was taken. 

PROJECTION LAMP. —An arc lamp provided with adjust¬ 
ments necessary to maintain the light source in correct rela¬ 
tion to the optical train of the projector. 

PROJECTIONIST. —A person who makes the projection of 
motion pictures his or her profession, trade or business. 
More particularly the title is applied to ambitious, energetic 
men of recognized ability in both practical projection and in 
technical knowledge as applied thereto. 

PROJECTOR, MOTION PICTURE.— A combination of a 
light source, its housing, an optical train and a mechanism 
and a supporting base, with the necessary means for adjust¬ 
ment of the various elements with relation to each other, 
the whole being used for the projection of motion pictures. 

PROJECTOR MOTOR SWITCH.— The switch attached to a 
projector by means of which the circuit operating its driving 
motor is opened or closed. 

PROJECTOR TABLE SWITCH.— The switch attached to 
the projector by means of which the projector light source cir¬ 
cuit is opened or closed. 

PUSH BUTTON. —A single pole contact switch for low 
voltage circuits which is operated by pushing a button. 

QUICK BREAK SWITCH.— A switch operated l#y a spring 
in such way that the contact is broken instantaneously. 

QUIET ARC— An electric arc which is noiseless in opera¬ 
tion. 

RACING— As applies to a motor or dynamo, the accelera¬ 
tion of speed which occurs when the machine is suddenly 
relieved of its load. 

RADIUS. —A straight line drawn from the center of a circle 
to any.part of its circumference. The distance from the cen¬ 
ter of a circle to its circumference. Half the diameter of a 
circle. 

RAIN. —Scratches in film which when filled with dirt be¬ 
come semi-opaque and have the appearance of “rain” in the 
projected picture. 

RATIO OF INTERMITTENT MOVEMENT.— The ratio of 
the time the intermittent sprocket is in movement to the time 
it is at rest during each cycle of the intermittent movement 


40 


HANDBOOK OF PROJECTION FOR 


action. It is properly expressed in degrees. A 60 degree 
movement would be one in which the driven member is in mo¬ 
tion during 60 degrees of the revolution of the driving mem¬ 
ber, hence the intermittent sprocket is in movement during 
that portion of the cycle. It would correspond to a 5 to 1 
movement, in which the total period is divided into 6 equal 
periods, during one of which the intermittent sprocket is in 
movement. Similarly a 6 to 1 movement would correspond to a 
50 (about) degree movement, the total period or cycle being 
divided into 7 periods. 

RATIO OF TRANSFORMATION.— In a transformer it is 
the ratio of the number of turns in the primary coil to the 
number, of turns in the secondary which establishes the rela¬ 
tion of the voltage and current of the secondary to the volt¬ 
age and current received by the primary. The relation of pri¬ 
mary and secondary turns is expressed as follows: Primary 
voltage: secondary voltage = primary turns: secondary turns. 
Primary current: secondary current = secondary turns: pri¬ 
mary turns. If there be more turns of wire in the primary than 
in the secondary the secondary voltage will be reduced and 
the secondary amperage increased, and vice versa. If there 
be 10 times as many turns in the primary coil as in the secon¬ 
dary coil, then the ratio will be 10 to 1, and the secondary 
voltage will be only l/10th that of the primary, while the am¬ 
perage will be 10 times greater. It will thus be seen that, 
allowing for no loss in the transformer, the wattage of pri¬ 
mary and secondary is always equal. 

REACTANCE COIL.-See “Choking Coil.” 

RECEPTACLE. —A wall socket for an incandescent lamp. 

REEL. —The flanged spool upon which film is wound for 
shipping and for use in projection. 

REEL OF FILM. —The fojptage carried upon a single reel 
built to carry 1,000 feet of film, when the said reel is approxi¬ 
mately full. 

REFLECTION. —The change of direction of a light ray 
when it meets a non-absorbing surface and is thrown back. 
See P. 572 Optic Projection. 

REFRACTION.— See page 127. 

REFRACTIVE INDEX. —When a ray of light passes 
obliquely from one medium into another of different density, 
the ratio between the lines of the angle of incidence and 
angle of refraction is known as the “index of refraction” 
of the second medium with respect to the first. 


MANAGERS AND PROJECTIONISTS 41 

RELIEF PROJECTIONIST. —The projectionist who works 
a short shift to relieve the regular projectionist during meal 
times or for some other purpose. 

REMOTE CONTROL. —The control of apparatus from a 
point some distance removed therefrom, as, for instance, a 
motor generator located in a basement may be started, stopped 
and controlled from the projection room. 

RESIDUAL MAGNETISM. —As applies to a dynamo, the 
magnetism retained by its field magnet when the machine is 
not in operation. 

RESISTANCE. —That property of an electrical conductor 
which opposes the flow of current. Also the term frequently 
applied to a rheostat. 

RESISTANCE COIL. —A coil of resistance wire, such as is 
used in making up the resistance of a wire coil rheostat. 

RESISTANCE LOSSES. —Losses due to the resistance the 
current encounters in opposition to its flow. See “Copper 
Loss.” 

RESISTANCE OF ARC. —The resistance offered by the floor 
of the positive crater in the arc stream and the tip of the 
negative carbon. 

RESISTANCE WIRE. —Wire composed of special alloy de¬ 
signed to offer a fixed pre-determined resistance to current 
flow. It is used for various kinds of rheostats. 

RETURN WIRE. —Same as “Negative,” which see. 

REVERSIBLE MOTOR. —An electric motor which may be 
run in either direction, as in street car work. 

REWINDER. —A device for transferring film from one reel 
to another. 

REWINDING. —The process of transferring film from one 
reel to another. This process is necessary each time a film is 
projected in order to change the beginning of the film from 
center to outside of film roll. 

RHEOSTAT. —A device consisting of several units of re¬ 
sistance which are electrically coupled in such way that the 
current must pass through the entire length of each unit in 
order to reach the next. A rheostat may be adjustable, so 
that the current may be forced through the entire series of 
resistance units, or some of them be cut out, at the will of the 
man in charge, or it may be non-adjustable so that the current 
must pass through the entire series of coils or grids. The 
resistance of a rheostat may be made up of coils of resistance 
wire or banks of cast iron resistance grids. 


42 


HANDBOOK OF PROJECTION FOR 


RING OILING. —A method of oiling machinery bearings. A 
ring of considerably greater diameter than the shaft is hung 
upon it, the lower portion of the ring extending down into a 
reservoir of oil under the bearing, so that the ring being 
revolved by the shaft, oil is carried up by it to the bearing. 

ROCKER ARM. —That part of a dynamo or motor to which 
the brush holders are attached, which may be rocked back 
and forth to shift the position of the brushes around the 
commutator to the point of least sparking. 

ROTARY CONVERTER. —A dynamo for generating both 
direct and alternating current. Remembering that current 
generated in D. C. dynamo armatures is A. C., it will be 
seen that if the armature current be led to collector rings A. 
C. will be obtained. If the machine be run as a D. C. motor 
A. C. may be had at the collector rings, and if run as a syn¬ 
chronous A. C. motor, direct current may be obtained from 
the commutator. The rotary converter may also be defined 
as a rotary transformer. 

ROTARY FIELD. —The field created by a combination of 
alternating currents differing in phase, so that if an armature 
of suitable winding be rotated therein the field will rotate be¬ 
cause of induced currents. The action of an induction motor 
depends upon the creation of a rotary field. 

ROTOR. —In a dynamo or motor, the part which revolves. 

R. P. M. —Revolutions per minute. 

R. P. S. —Revolutions per second. 

RUBBER. —As applies to insulation, rubber may be used in 
different ways. In the form of a rather thin, plastic mass it 
may be placed on a wire and vulcanized. It is used for insu¬ 
lating tape, and as a vulcanite or an ebonite it is used for 
switch handles, insulating tubing, etc. 

R. C. —Rubber Covered. 

RUBBER COVERED WIRE.— See page 80. 

SATURATION. —As applies to a magnet, the highest power 
to which the magnetic flux can be raised. The point at which 
the metal will receive no further magnetism. 

SCREEN.— In projection, the surface to which the picture 
(image) is projected. 

SCREEN, METALLIC SURFACE. —A screen surface con¬ 
sisting for the most part of metallic powder, such as 
aluminum. Tin foil has also been used with some success.- 

SCREEN, MIRROR. —A screen consisting of a plate glass 
mirror, the surface of which has been ground to break up the 
regular reflection. 


MANAGERS AND PROJECTIONISTS 


43 


SCREEN, SEMI-REFLECTING. —A term commonly used 
to describe metallic and other brilliant surface screens, which 
to greater or less extent give both diffuse and regular reflec¬ 
tion. 

SCREEN, DIFFUSING. —A screen which has high powers 
of diffusion of light. 

SCREEN, CALSOMINED. —A backing of suitable material, 
usually plaster or cloth, which is coated with calsomine. See 
page 229. 

SCREEN, PAINTED. —A backing of suitable material the 
surface of which is painted, either with a mixture of white 
lead and zinc, or white zinc, mixed flat. See page 227. 

SCREEN BORDER. —A border of flat black or other dark 
color surrounding the picture, for which it serves as an out¬ 
line. See page 240. 

SCREEN BRILLIANCY.— The apparent brilliancy of the 
screen surface as viewed from the auditorium; also the degree 
of brilliancy per unit of area of the screen surface as shown 
by photometer measurements. 

SCREEN SETTING. —The immediate surrounding of the 
screen. 

SECONDARY COIL. —In a transformer, a coil of insulated 
wire in which the secondary current is induced. See “Primary 
Coil.” - 

SECONDARY CURRENT. —The current induced in the 
secondary coil of a transformer. The current delivered to 
a projection lamp by an Economizer, Inductor or Compens- 
arc. 

SECONDARY E. M. F. —The voltage of the current induced 
in the secondary coil of a transformer. 

SELF CONTAINED. —A term employed to describe a ma¬ 
chine the essential parts of which are all contained in one 
frame, or in one foundation, 

SELF OILING BEARINGS. —Machine bearings which are 
oiled automatically by the operation of the machine itself, 
the oil usually being contained in an oil well or reservoir 
located beneath the bearing, from which it is delivered to 
the bearing by suitable means. See “Ring Oiling.” 

SERIES.— As applies to electrical machines, lamps or de¬ 
vices, a connection in such way that the current must pass 
through two or more of them in succession in its passage 
from positive to negative. 

SERIES WOUND DYNAMO.— A dynamo in which the field 
magnets are wound with a few turns of heavy wire which is in 


44 


HANDBOOK OF PROJECTION FOR 


series with the armature and the external circuit, so that the 
entire output of the armature must pass over the field coils. 

SERIES-SHUNT WOUND DYNAMO.— A dynamo the field 
magnets of which carry both shunt coils and series winding. 

SERIES-PARALLEL CONNECTION. —A circuit containing 
groups of current-using devices connected in parallel (mul¬ 
tiple) with each other, the groups themselves being connected 
in series. A series multiple connection. 

SERIES WOUND MOTOR. —A motor wound the same as 
a series wound dynamo, insofar as concerns its field coils. 

SERVICE WIRES. —Wires leading into the consumer’s 
premises from the street mains. 

SHELLAC. —A resinous varnish the liquid component of 
which is alcohol. It is used as an insulator in certain classes of 
work. It may be thinned with wood or denatured alcohol. 

SHORT CIRCUIT. —Commonly termed a “Short.” In the 
common acceptance of the term a fault in an electric circuit or 
apparatus, usually due to defective insulation, by means of 
which the current follows a low resistance by-path to a con¬ 
ductor of opposite polarity, and either inflicts damage, or is 
wasted in so doing. 

SHUNT. —In an electric circuit a branch conductor joining 
the main circuit at two points, forming a parallel path, so that 
the current is divided, a portion passing through the main cir¬ 
cuit and a part through the branch. 

SHUNT CIRCUIT. —Same as “Shunt,” which see. 

SHUNT COIL. —A coil joined in shunt to the main circuit, 
as the field magnet shunt coil of a dynamo or motor. 

SHUNT WOUND DYNAMO.— A generator having its field 
coil connecting in shunt with the main circuit. 

SHUNT WOUND MOTOR.— A motor having its field coil 
connected in shunt with the main armature circuit. 

“SIDE” OF 3-WIRE CIRCUIT.— In a 3-wire system the 
neutral wire and one (either) outside wire forms one “side” 
of the system. 

SINGLE POLE SWITCH. —A switch which controls only 
one of the wires of a circuit. A knife switch having only one 
blade. 

SINGLE THROW SWITCH.— A knife switch which makes 
and breaks on one set of contacts only. 

SOLID CARBONS. —Carbons having no “core.” Carbons 
having a presumably uniform density throughout. 


MANAGERS AND PROJECTIONISTS 


45 


SPEED INDICATOR. —As applied to projection, a device 
designed to indicate the speed of projection on a direct reading 
dial. 

SPHERICAL ABERRATION.— See page 129. 

SPHERICAL CANDLE POWER.— The candle power of a 
light source measured in every direction. 

SPLICING. —Joining two sections of a film or wire together. 

SPLIT PHASE. —A single phase current divided into poly¬ 
phase by means of a phase splitting device. See “Phase 
Splitter.” 

SPROCKET. —A revolving toothed roller or wheel by means 
of which movement of film through projector is caused and 
controlled. 

SPLIT PHASE MOTOR. —A single phase induction motor 
provided with a phase splitting device for starting. 

STANDARD CANDLE. —A sperm candle so made that it 
consumes 120 grains of wax an hour. 

STANDARD FILM.— See page 130. 

STAR. —As applies to projection, the member of a star and 
cam type of intermittent movement to which movement is 
imparted by the actuating cam. The part of an intermittent 
movement of the star and cam type which is attached to the 
intermittent sprocket shaft. 

STEEL. —A compound of iron, about 3 per cent, of carbon 
and usually small quantities of silicon and manganese. It is 
the carbon which causes the metal to harden when cooled 
suddenly from red heat, and to soften again when cooled 
slowly. 

STEP-DOWN TRANSFORMER. —A transformer which re¬ 
duces the primary voltage and increases the amperage in 
proportion. 

STEP-UP TRANSFORMER. —A transformer which de¬ 
livers higher secondary voltage than the impressed primary 
voltage, decreasing the amperage in proportion. 

STEREO. —Contraction of the word Stereopticon. 

STEREOPTICON. —A light source and optical train, to¬ 
gether with the necessary housing and mechanism for holding 
and adjusting the lenses, for the projection of still pictures 
(transparencies) to a screen. 

STOPPING DOWN. —In projection, the act of reducing the 
diameter of the free opening of a lens. 

STORAGE BATTERY— A form of battery which, when 
subjected to the action of an electric current undergoes cer¬ 
tain chemical changes, enabling it to produce electric power 


46 


HANDBOOK OF PROJECTION FOR 


in proportion to the energy consumed in producing the 
change. It is erroneously called a “storage” battery. As a 
matter of fact there is no actual electricity in a “storage” 
battery, but instead there is an ability to produce or generate 
electricity. 

STRANDED WIRE. —A wire composed of several smaller 
wires, usually twisted together. 

STRANDED WIRE, ASBESTOS COVERED.— A conductor 

made up of a large number of very small wires (usually No. 
30 or 31 B & S) in order to obtain flexibility, covered with as¬ 
bestos insulation so that it may be used in places where the 
heat is too great to allow of the use of ordinary insulation. 

STRIKING AN ARC. —The act of bringing the carbons of 
an arc lamp into contact and separating them again in order 
to obtain an electric arc. 

A. S. W. G. —Abbreviation for American Standard Wire 
Gauge, commonly known as the “B and S” wire gauge. 

SYNCHRONISM. —A relation as to time of the pressure 
waves of two or more alternating currents when combined 
in an electric distribution system. See Fig. 5. 

SYNCHRONIZING. —So regulating the operation of two 
A. C. generators that they will be identical and simultaneous 
both in phase and frequency. 

SYNCHRONOUS MOTOR.— An A. C. motor which must be 
brought up to speed and into step with the phase of the gen¬ 
erator before being connected direct to the circuit. Such a 
motor is to all intents and purposes an ordinary A. C. genera¬ 
tor run as a motor. 

TAKEUP. —A device by means of which the film is wound 
upon a reel as fast as it comes from the projector mechan¬ 
ism. 

TAKEUP PULL. —The pull exerted by the takeup tension. 
It must not exceed 15 ounces at the periphery of a 10-inch 
reel, or 16 ounces on an 11-inch reel. 

TAKEUP TENSION.— See “b” under “Tension.” 

TAPED JOINT. —A wire joint or splice, wrapped with in¬ 
sulating tape. 

TAPE, INSULATING.— See “Insulating Tape.” 

TENSION. —As applied to projection (a) the pressure ex¬ 
erted by the tension springs, either through the tension shoes 
or direct, upon the film at the aperture, (b) The tension ex¬ 
erted by a spring upon two friction discs for the purpose of 
revolving the film reel in the lower magazine, providing slip¬ 
page so that the reel, although driven by a power having 


MANAGERS AND PROJECTIONISTS 47 

steady speed, may revolve at differential speed, gradually 
slowing up as the film roll increases in size. 

TENSION SHOES. —Metal bars upon which the tension 
springs bear which themselves bear directly on the film and 
provide braking friction to stop film over aperture. 

TENSION SPRINGS. —The springs which provide braking 
action to stop the film over the aperture at the completion 
of the intermittent movement. 

THREE-PHASE.— See page 18. 

THREE-WIRE CIRCUIT. —A circuit in which all three 
wires O’f a three-wire system are used. 

THROW. —See “Projection Distance.” 

THREE-WIRE SYSTEM.— See page 85. 

THUMB MARK. —A mark on the lower left hand corner of 
a stereo slide when the slide is held so as to be read against 
the light. Thumb mark is on the face (cover glass) side of 
the slide. 

TORQUE.— The pulling force which tends to rotate, as the 
rotating of a motor armature. 

TRAILER. —A short length of opaque film attached to the 
end of a reel of film so that projection may proceed up to the 
end of the film proper without showing white light upon the 
screen. 

TRANSFORMER. —A device for transforming A. C. of high 
voltage to a lower voltage and increased amperage, or vice 
versa. See page 544. 

TRAVELING ARC. —An unsteady arc, particularly one in 
which the point of highest illumination in the crater moves 
about, usually due to faulty carbons. 

TRIPLE POLE, SINGLE THROW (T. P. S. T.) SWITCH. 
—A knife switch with three blades, but which makes and 
breaks on one set of contacts only. 

TWO-PHASE CURRENT.— See page 18. 

TWO-PHASE MOTOR.— An induction motor which, in¬ 
stead of having a single field winding, has two separate wind¬ 
ings, each taking current from a single phase circuit of the 
same frequency, but differing in phase by one-quarter of a 
period. A motor made to operate on two-phase lines. 

TWO-PHASE SYSTEM. —A system supplied with two al¬ 
ternating currents of the same frequency, but differing in 
phase by a quarter of a period. It may be supplied by two 
separate two-wire circuits, or by a three-wire system in 
which one wire is common to the two currents. 


48 


HANDBOOK OF PROJECTION FOR 


TWO-WIRE SYSTEM— A system in which only two wires 
are employed. 

ULTRA VIOLET RAYS.— Rays of light existing beyond the 
violet light of the visible spectrum. These rays have a vmra- 
tion in excess of eight hundred billion per second. 

UNBALANCED LOAD. —As applies to the 3-wire system, a 
condition in which more current is consumed on one side of 
the system than on the other, which has the effect of com¬ 
pelling one generator to carry a heavier load than the other. 

UNDERWRITERS' RULES.— See “National Electric Code.” 

USEFUL LIFE. —A term applied to many things, but in 
electrics particularly to incandescent lamps, which deteriorate 
with age. It is the time an incandescent lamp will burn before 
its output of light has decreased more than 20 per cent. 
When a lamp has fallen below 80 per cent, of its rated c. p. 
it is the part of true economy to replace it with a new one. 

VOLATILIZATION. —In projection, the transforming of 
carbon into vapor through heat. 

VOLT. —Unit of electrical pressure. See page 50. 

VOLTAGE DROP. —The drop in voltage due to the resis¬ 
tance of the conductors. Voltage drop exists in every circuit. 
See “Copper Loss.” 

VOLT-AMMETER. —An instrument for measuring current 
consumption in watts. 

VOLTMETER. —An instrument of high resistance for meas¬ 
uring electrical pressure. 

WATER GLASS. —Soluble glass. Used as a binder for 
carbon cores. It is the residue of water glass which forms 
the white, light weight ash with which the interior of the 
lamphouse becomes coated. 

WATT. —The practical unit of electrical power. See page 53. 

WATT HOUR. —The energy consumed when one watt of 
electrical energy has been used for one hour. 

WATT-HOUR METER. —A meter used for measuring elec¬ 
trical consumption in watt hours. 

WATTS PER CANDLE POWER.— The specific consump¬ 
tion of an electric lamp is its watt consumption per mean 
spherical candle power. In connection with incandescent 
lamps, the term “watts per candle power” is used commercially 
to denote the watts consumed per mean horizontal c. p. 

WESTERN UNION WIRE JOINT.— See figure 26. 

WIRE GAUGE. —A gauge for measuring round wires ac¬ 
cording to an arbitrary standard. See page 78. 


MANAGERS AND PROJECTIONISTS 


49 


WORKING APERTURE. —In projection, that portion of 
the aperture of a lens which is actually in use in the sense that 
it is contributing to the improvement of the finished screen 
result. 

WORKING DISTANCE.— The distance from film to first 
surface of a projection lens when it is adjusted to actual 
working conditions. See “Back Focus.” 


AN EMPLOYEE IS PAID 
FOR THREE THINGS, VIZ: 
TIME, STRENGTH AND 
KNOWLEDGE. THE FOOL 
CAN GIVE THE FIRST, 
THE DULLEST OF WIT 
MAY GIVE THE FIRST 
TWO, BUT IT IS THE 
WORTH-WHILE MAN OF 
INTELLIGENCE AND 
BRAINS WHO CAN 
SUPPLY THE THIRD AND 
WHO GETS THE REAL 
MONEY AND THE BIG 
POSITION WHEN IT 
COMES. 



50 


HANDBOOK OF PROJECTION FOR 


Electrical Terms and Their 
Meaning 

T HERE are a few electrical terms with which the pro¬ 
jectionist comes into quite intimate contact in his daily 
work. It is essential that he have a thorough under¬ 
standing of what they actually represent to the end that he 
be able to use them intelligently in the various calculations 
arising from time to time in his work. 

POLARITY. —Polarity and Potential mean the same thing. 
When wires are attached to opposite terminals of the same 
dynamo there is present in these wires an electrical condition 
which enables them to perform work. Properly cjnnect them 
to an electric motor and the energy in or on these wires will 
cause its armature to rotate and exert a pull and thus pro¬ 
duce power. 

Attached to a lamp the energy in or on these wires will 
cause the filament or the carbons thereof to become white 
hot, and thus produce light. 

This electrical condition is termed “polarity” or “potential.” 
It is, or it represents the electrical affinity which the posi¬ 
tive wire of an electric circuit has for the negative wire of 
the same circuit, or the negative wire of any circuit attached 
to the same dynamo. It represents the inclination of the 
electric impulse to “flow” from positive to negative, which 
same is termed “current flow.” See Page 3. 

POSITIVE AND NEGATIVE AS APPLIES TO D. C.— 
When wires are charged with direct current one wire is con¬ 
tinuously positive and the other negative. 

POSITIVE AND NEGATIVE AS APPLIES TO A. C.— 
When wires are charged with alternating current each wire 
of the circuit is alternately positive and negative many times 
every second. If it be 60 cycle current, then each wire is 
positive 60 times and each wire negative 60 times per second. 

VOLTAGE OR ELECTRO MOTIVE FORCE (E. M. F.). — 
Electric current is usually treated as having both pressure 
and volume. In its action as relates to these attributes, as 
well as regards the item of friction, electricity is very similar 


MANAGERS AND PROJECTIONISTS 51 

to, and may be compared with water, but it must be remem¬ 
bered that the similarity exists in similarity of action only. 

Water may be subject to physical examination. We can 
feel it, watch its action and weigh it. On the other hand, 
electricity is an absolutely impalpable substance—if we may 
even call it a substance. It apparently is without weight. 
We cannot see it, except in the form of light, which is not 
the current itself but a product of its action. We cannot feel 
it, except in the form of a “shock” occasioned by the current 
passing through the tissues of the body. 

Voltage corresponds in effect, or in its action, to the pres¬ 
sure of water in a pipe, or to the pressure of steam in a boil¬ 
er. A dry battery, such as is used for electric bells, has a 
pressure of approximately one volt. It imparts that pressure 
to wires connected to its terminals, so that if you attach two 
wires to such a battery, they will, at any portion of their 
length, have an electrical pressure of one volt. If you con¬ 
nect the zinc of a second battery with the carbon of the first 
battery by means of a short piece of wire, and then attach 
two other wires to the two remaining binding posts, you will 
have what is known as “series” connection, and a resultant 
pressure of two volts between the two last named wires. A 
third battery connected in series would raise the pressure to 
three volts, and so on indefinitely. 

Instead of using batteries for producing light and power, 
which would be entirely impractical, we use a machine called 
a dynamo, each one of which is designed and built to produce 
a certain voltage, which may be anywhere from one to 500 
volts D. C., or from one to 6,000 volts A. C. 

Remember that voltage corresponds to pressure, and is 
similar in its action to pressure in a steam boiler, but that 
voltage acts only between the positive and negative wires of 
the dynamo or battery which generated it, and that the posi¬ 
tive attached to one generator has no affinity or attraction 
to or for the negative attached to another dynamo, or for the 
ground, except as it offers a path to the negative of the gen¬ 
erator to which the positive is attached. Get this fact firmly 
fixed in your mind. Ninety-nine out of every hundred non¬ 
electricians believe current generated by a dynamo seeks to 
escape into the ground. This is not so, except insofar as the 
ground may offer a path of electrical conductivity between 
two wires of opposite polarity. See page 6. 

AMPERE is the term used to denote quantity. It repre¬ 
sents the volume of current flowing through, or along a wire, 


52 


HANDBOOK OF PROJECTION FOR 


just as gallons or barrels represent the quantity of water 
flowing through a pipe, or cubic inches the volume of steam 
flowing. As a matter of fact we do not actually know that 
anything flows in or along the wire of an electric circuit. 
Eminent theoretical electricians say there is an actual flow; 
other equally eminent theoretical electricians say there is 
not, but that what we consider as current flow is really a 
“molecular bombardment.” With these highly technical 
questions, however, we have no concern. For our purpose it 
is sufficient to say that the current flows along the wires, ex¬ 
actly as water flows through a pipe. 

HOW WORK IS ACCOMPLISHED.— The work performed 
is accomplished by voltage, or pressure, working through am¬ 
perage, or volume. When a water wheel is turned by water it 
is not the water but the pressure which is consumed. True, 
the work is sometimes done by falling water, in which case the 
weight of the water amounts to and is the same as pressure, 
and in that case it is the pressure produced by gravity or 
weight which does the work. It, therefore, follows that the 
higher the pressure or voltage the greater the amount of 
work a given current volume or number of amperes can 
accomplish. 

For instance, if we supply an engine with steam at fifty 
pounds pressure, there will be a certain, definite number of 
cubic inches of steam used at each stroke of the piston, and 
a certain definite number of foot-pounds of work will be ac¬ 
complished. But if, without changing anything else, we raise 
the steam pressure to one hundred pounds, the engine, while 
still using precisely the same number of cubic inches of steam 
at each stroke of the piston, will perform twice as many 
foot-pounds of work. In this case, while the volume of steam 
used remains unaltered, the pressure is doubled, in both cases 
the pressure is entirely consumed, but the volume of steam 
remains and is not consumed. The same power would be 
produced by the lower pressure if the area of the piston be 
doubled, since twice as much pressure would be made avail¬ 
able through increase of volume; but again it would be pres¬ 
sure, not volume, which would be consumed. 

It is the same with electric current. Ten amperes of cur¬ 
rent at 50 volts represents a certain, definite amount of en¬ 
ergy. Ten amperes at 100 volts represents just twice as 
much, though it is also true that twenty amperes at 50 volts 
would amount to the same thing in power production. The 
point we seek to make is that amperage or volume is merely 


MANAGERS AND PROJECTIONISTS 53 

the vehicle through which pressure or E. M. F. works, and 
that in the production of power in any form it is voltage 
(pressure) and not amperage (volume) which is consumed. 

In a steam engine, with the steam at given pressure we 
may increase the power of the engine by either increasing 
the area of the piston or the length of its strokes or by in¬ 
creasing the pressure of the steam. In a water motor we may 
increase the capacity to do work either by increasing the 
size of the motor or the pressure of the water. The same 
thing holds true with electricity. We may increase its ca¬ 
pacity to do work either by increasing the volume of current 
(amperage) or by increasing the voltage. To perform a given 
amount of work with a low pressure (voltage) a large volume 
(amperage) is necessary, but if the voltage be high the same 
amount of work can be performed with much less volume of 
current. The horse power of work performed by electric 
current is represented by the voltage times the amperes di¬ 
vided by 746.H.P. = Volts x Amperes 746. 

OHM. —In passing through a pipe water encounters re¬ 
sistance by reason of the rough sides of the pipe, as well as 
by reason of the internal resistance of the water itself. This 
resistance tends to retard the flow. Precisely the same is 
true with electricity. In passing through a wire electric 
current encounters resistance, and this resistance tends to re¬ 
tard the flow of current. It is measured in ohms, the defini¬ 
tion of which is given on page 35. 

The effect of resistance is to produce heat. In other words 
power consumed in overcoming resistance is transformed into 
heat. In a water pipe the resistance increases as the volume 
of water passing through a pipe of given diameter is in¬ 
creased, or as the diameter of the pipe is made smaller with 
relation to the volume of water flowing. The same thing is 
true of current. Having a wire of given diameter its resist¬ 
ance increases as the current flow becomes greater, and de¬ 
creases as the current flow becomes less, or, having a given 
current flow, the resistance decreases as the diameter of the 
wire is made greater, or its length is decreased. 

WATT. —Watt is the unit used to measure the amount of 
electrical energy expended—the amount of work actually per¬ 
formed. It is found by mutiplying the voltage by the number 
of amperes, and is transformed into horsepower by dividing 
that result by 746, since 746 watts is equal to one electrical 
horsepower. For example: If we have 10 amperes at 110 
volts the amount of energy expended would be equal to 110 x 


54 


HANDBOOK OF PROJECTION FOR 


10 = 1100 watts, which, divided by 746, equals 1.47 h. p. If, 
on the other hand, we use 110 amperes at 10 volts, the result in 
power would be the same. But if we use 10 amperes at 
10,000 volts we then would have 10,000 x 10 = 100,000 watts, 
which, divided by 746 equals 134 h. p. 

USE OF ELECTRICAL TERMS IN CALCULATIONS.—In 

projection rooms not equipped with a reliable voltmeter and 
ammeter it will be difficult for the projectionist to make in¬ 
telligent calculations, since in order to find a desired quan¬ 
tity, be it voltage, amperes or ohms, he must know the value 
of the other two. In order to accurately calculate the num¬ 
ber of amperes flowing in a circuit it is necessary to know 
exactly the number of ohms resistance the circuit offers (in¬ 
cluding wires, appliances, etc.) and the exact voltage. 

It is, however, highly desirable that the projectionist under¬ 
stand how to make electrical calculations, at least insofar as 
applies to his projection circuit, since under some circum¬ 
stances such knowledge will be necessary to intelligent work. 

The projectionist must firmly fix in his mind the fact that 
where the projection circuit is concerned the resistance does 
not lie wholly in the rheostat, or whatever takes its place. 
The wires, carbon-arms and carbons usually offer compara¬ 
tively slight resistance, but a very considerable portion of 
the total resistance of a projection circuit is in the arc itself. 
Under usual conditions the resistance of the wires, carbon- 
arms and carbons may, for the purposes of calculation, be 
neglected, but unless the resistance of the arc itself be taken 
into consideration, very serious error will result. 

When making electrical calculations it is customary, for 
the sake of brevity, to use the letters E, C, and R, in which 
E stands for “electromotive force,” which is merely another 
name for voltage; hence E stands for voltage; C stands for 
current flow, meaning amperes ; hence C stands for amperes; 
R stands for resistance in ohms; hence R stands for ohms. 

The projectionist should also remember that in a common 
fraction the horizontal line always means “divided by,” thus 
1/2 really means 1 -j- 2. To divide 1 by 2 we put down the 1, 
followed by a period, called a “decimal point” and then add 
ciphers thus : 1.00. We now have 1.00, with a decimal point 
between the one and the two O’s. In dividing 1 by 2 we only 
need one cipher, thus 1.0 and 1.0 -s- 2 = .5, which is exactly 
the same thing as 5/10, or 1/2. The rule is to count the fig¬ 
ures or ciphers to the right of the decimal point in the num¬ 
ber being divided, and then, beginning at the last figure of the 


MANAGERS AND PROJECTIONISTS 


55 


result, count an equal number, and place the decimal to the 
left of the last figure counted. If there are not enough fig¬ 
ures in the result to do this, add enough ciphers on the left. 

When dealing with formulas, E/C means that the quantity 
represented by E is to be divided by the quantity represented 
by C, E being the voltage and C amperes. If there be two or 
more quantities above or below the line, with no sign between 
them, it means that they are to be multiplied together, thus: 
E 

— means that E (volts) is to be divided by C (amperes) mul- 
CR 

E-15 

tiplied by R (ohms). - means that after 15 has been sub- 

C 

tracted from the quantity represented by E (volts), the re¬ 
mainder is to be divided by the quantity represented by C 
(amperes). The student will be greatly benefited if he will 
practice writing out formulas of this kind in letters, after¬ 
ward substituting quantities in figures and working them 
out. 


Ohms law sets forth the fact that the number of amperes 
flowing is equal to the voltage divided by the resistance in 

E 

ohms. We therefore have — = C, or in other words, volts 


divided by ohms equals amperes. It then follows that if — = C, 

R 

E 

C multiplied by R must equal E. It also follows that — = R. 

C 

It works out as follows: We know that the ordinary 110 volt, 
16 c. p., carbon filament incandescent lamp requires approxi¬ 
mately one-half ampere of current to bring it up to candle 


power. What is its resistance? Using the formula — = R, 

C 


110 volts 

substituting figures, we have-— 220, the number 

.5 of an ampere 

of ohms resistance in the filament of the lamp. Again applying 
E U0 

the formula — = C, we have-= -5, or y 2 , as the ampcr- 

r 220 



56 


HANDBOOK OF PROJECTION FOR 


age 110 volts will force through 220 ohms resistance. All this 
seems simple enough of understanding and application, but to 

E 

make it yet more plain we will consider the formula — = R, 

C 

which means voltage divided by amperes equals ohms. If 
the voltage be 50 and the amperes 10, then E would be 50, C 
would be 10, and R would be 50 10 = 5. If the voltage 

were 110 and the amperage 5, then E would be 110, C would 
be 5, and R would be 110 5 = 22 ohms. 

When, however, we come to consider the projection arc cir¬ 
cuit a new element enters in the shape of the resistance of 
the arc itself, and if we propose to be absolutely accurate w'e 
must consider also the resistance of the carbon arms, wires, 
etc. That degree of refinement, however, is seldom, if ever, 
necessary in a projection circuit calculation. 

In leaping the gap between the carbon tips of the arc lamp 
the current encounters high resistance. In overcoming re¬ 
sistance voltage is consumed, as will be more thoroughly set 
forth and explained under “The Light Source.” In other 
words, when current flow is opposed by resistance, and that 
resistance is overcome, there is a consequent drop in pres¬ 
sure or voltage; pressure having been consumed in the process. 

For reasons not necessary to enter into at this time, the 
D. C. arc, for a given amperage, is longer than the A. C. arc. 
It therefore follows that its resistance will be higher. The 
accepted theory is that all voltage is consumed at the arc. 
Whether or not this is true is a highly technical question, 
which it would be unprofitable to discuss in this book. 

We shall accept the theory as stated. It then follows that 
the rheostat, or whatever takes its place, must reduce the volt¬ 
age to just that pressure which the resistance of the arc will 
consume when the arc is burning normally. 

ARC VOLTAGE CONSTANTS.—Under varying conditions 
projection arcs will operate at their best at different voltage 
drop. Tables on page 395 and 400 are as reliable as any 
though various carbon combinations would undoubtedly alter 
the results as set forth therein in considerable degree. 

The figures in tables 21 and 22 are NOT given as an accurate, 
unvarying factor. They are designed as a fairly ac¬ 
curate guide only. They may be safely used in figuring neces¬ 
sary resistance for a temporary set-up. 

And now let us illustrate the method of applying this 
knowledge in practice. 


MANAGERS AND PROJECTIONISTS 


57 


Taking a 60 ampere arc, for example, what is its resistance? 

Accepting for the sake of simplicity in figuring the constant 
60 volts as approximately correct for a 60 ampere arc, we 
E 60 

then have — = R. Substituting figures we then have — = R, 
C 60 

and 60 60 = 1 ohm, which is the arc resistance, or the re¬ 

sistance necessary to consume 60 volts. 

Let us prove this. Suppose the line voltage to be 110. The 
total resistance necessary to allow 60 amperes to pass must 
E 

then equal — = R the voltage divided by amperage; hence 
C 

amperes being 60 and voltage 110, the resistance will be 
110 - 5 - 60 = 1.833 ohms. We have already seen that the re¬ 
sistance of the arc is 1 when the arc voltage is 60. Subtract¬ 
ing the arc voltage from the line voltage (110—60) gives 50 
as the drop in voltage there must be across the rheostat. In 
other words, there must be 50 volts of electric energy con¬ 
sumed, or “used up” in the rheostat, which will appear in the 
form of heat. 

E 

Again applying the formula — = R, we have 50 -s- 60 = 

C 

.833+ (the + sign meaning that the division could be carried 
further) as the ohmic resistance of the rheostat. If we now 
add the resistance of the arc and the rheostat together (1 
plus .833) we shall have as a result 1.833, which corresponds 
to the total resistance necessary to allow 60 amperes to pass, 
the slight discrepancy as between 1.832 and 1.833 being due 
to the division being only carried to the fourth decimal point. 

If the amperage were more than 60, line voltage remaining 
the same, then the total resistance would be less, since volt¬ 
age divided by amperes (E -5- C = R) equals resistance, and 
the result obtained by dividing 110 by a number greater than 
60 is a less number of ohms. Conversely, if the amperage be 
less than 60 the total resistance necessary (arc and rheostat) 
would be greater. 

The higher the line voltage the greater must be the resist¬ 
ance to accomplish a given current flow, as wifi be seen by 
• E 

applying the formula — = R. 

C 


58 


HANDBOOK OF PROJECTION FOR 


FORMULA TO USE IN FIGURING ARC VOLTAGE.-In 

practice we amend the before named formula for general cal¬ 
culations in such a way as to automatically take care of volt¬ 
age drop, thus: Suppose we wish to calculate the necessary 
ohmic resistance of a rheostat to pass 60 amperes D. C. from 

E 

110 volt lines. Instead of using the — = R, we amend it thus: 

C 

E-55 

-= R, the “55” being the constant for voltage drop of 

C 

a 60 ampere D. C. arc. Substituting figures we would then 
110-55 

have - = .9166 ohms, and we thus at one operation 

60 

have the result sought. In using this latter formula we would, 
of course, use the voltage drop constant for the amperage 
used in each case. 

A. C. VOLTAGE DROP.—When figuring A. C. projection 
arc voltage drop we must use a different constant, consider¬ 
ably lower in value. See page 400. 

As an example of the possible actual practical value of 
knowledge, such as is contained in the immediate foregoing, 
suppose you are called upon to take charge of projection in a 
theatre employing a private 125 volt light plant, using 50 am¬ 
peres at the arc. You find the rheostats in bad shape and 
order new ones. Instead of ordering a 50 ampere, 110 volt 
rheostat you, discarding unintelligent guess-work, apply the 
E-50 

formula-= R, or, better still, measure the actual voltage 

C 

of the arc by disconnecting the voltmeter and touching one of 
the wire attached to its terminals to each carbon of the pro¬ 
jection lamp, when you have the arc burning normal. Sup¬ 
pose the voltmeter reads 52. You would then have the for- 
125-52 

mula -: = 1.46 ohms as the necessary resistance of a 

50 

rheostat to deliver exactly 50 amperes, under the conditions 
at your plant. Would you not rather be able to hand the 
manager an order for exactly what you want, and need, than 
an order which will probably result in your need being only 
met approximately? 





MANAGERS AND PROJECTIONISTS 59 

RULE O’ THUMB.—There is a very simple formula, easy 
of application, which combines the three formulas into one. 
It is called the “Rule of Thumb.” It is expressed for general 
E 

use as: - 

CR 

To use the formula you have but to cover the symbol or 
letter representing the quantity desired, and what remains 
will produce the answer, thus: Suppose we wish to ascertain 
the resistance in ohms. We cover up the “R” in the formula 
E 

and find that we have — remaining, which will give R, the 
C 

desired quantity. In using this formula on projection circuits 
the top letter must be expressed as E minus the arc voltage, 
the same as in the regular formulas. 


THE UNION MAY BE 
ABLE TO RAISE YOUR 
W A GES — YES , BUT IF 
YOU ARE REALLY 
WORTH MORE MONEY 
IT WILL BE VERY MUCH 
EASIER FOR IT TO DO SO. 



60 


HANDBOOK OF PROJECTION FOR 


Resistance 

T HE one thing which enters into all problems of the 
electrician and the projectionist is resistance. It is 
met with in every phase of electrical work and so far 
as the production of light be concerned, it is the very key¬ 
stone of the structure. 

When an electrical impulse passes through or over a wire 
it encounters resistance, which in its action is very similar 
to the resistance encountered by water in flowing through a 
pipe. 

When water flows through a pipe it encounters resistance 
which will be directly in proportion to the diameter and the 
length of the pipe, the roughness or smoothness of its interior 
surface, and the quantity of water flowing per minute. To 
some slight extent this resistance is the result of molecular 
friction within the water itself, but for the most part the 
friction is between the water and the walls or sides of the 
pipe. 

In a pipe of given diameter the resistance will increase 
with (1) increase of flow or volume of water, (2) increase of 
the length of the pipe and (3) with increase in roughness of 
the interior walls of the pipe. 

Conversely, resistance will decrease as the flow of water is 
diminished, the length of the pipe decreased or with increas¬ 
ing smoothness of the walls of the pipe. 

With a given flow of water, resistance will increase as the 
length of the pipe is increased, as the diameter of the pipe 
is made smaller or as the roughness of the walls of the pipe 
increases, or resistance decreases as the pipe diameter is 
increased, the pipe made shorter or as its walls become more 
smooth. 

Pressure is the motive power, either in the case of water 
or electricity, and resistance always consumes pressure, and 
consumes it precisely in proportion to the amount of resist¬ 
ance encountered. In the third edition of the handbook we 
explained this proposition by means of a diagram which we 
do not believe can be materially improved upon, hence it is 
herewith reproduced as Fig. 6. 


MANAGERS AND PROJECTIONISTS 61 

In Fig. 6 we see a large water main, upon the top of which 
is mounted a gauge registering 100 pounds pressure. To 
this main, pipes A B and C are connected. Pipes A and B 
have a half inch interior diameter. Pipe B is short, having 
a length, let us assume, of one foot. The water from it 
spurts out under high pressure, carrying itself almost hori¬ 
zontally over a considerable distance. Pipe A we will assume 
to have a length of 100 feet (in a drawing of this kind it is 
impossible to draw the pipe lengths in correct proportion and 
still make the details large enough to be understandable, 
therefore we assume pipe B to have a length of one foot and 
pipe A 100 feet, that being about the proportions that would 
give something approaching the results shown). You will 



observe two things with relation to pipe A: First, that where¬ 
as gauge 1 registers almost the same pressure as the gauge 
on the large main, gauge 2 registers very much less, and the 
water from pipe A spurts out with but little force. The rea¬ 
son for this is as follows : Pipe B is short, and whereas the 
water encounters high resistance because of being forced 
through with great rapidity, still there is not much length 
to the pipe, hence comparatively little of the total pressure 
is consumed in forcing the water through pipe B, even at 
high speed. Therefore it spurts out at the end of the pipe 
with great force. Pipe A, on the other hand, is 100 feet 
long, and the water in flowing through that length of half 
inch pipe would, at the same rate of flow, encounter 100 times 
the resistance offered by pipe B. Of course, the actual re¬ 
sistance encountered is not 100 times as great, because as 

















62 


HANDBOOK OF PROJECTION FOR 


pressure is consumed in overcoming the resistance of the long 
pipe the movement of the water is slowed down. In this 
we see the exemplification of the effect of added resistance 
due to increased length of pipe, diameter remaining the same. 

Now let us consider pipe C, which we will assume to have 
a total length of 10 feet of three inch, and two feet of half 
inch pipe. We observe that gauge 3 on pipe C registers es¬ 
sentially the same as does the gauge on the water main. This 
is because, since only the capacity of the half inch pipe at its 
end can flow, the water in pipe C is moving slowly, hence 
encounters very little resistance. In other words, pipe C is 
working far below its normal capacity. The short pipe at 
its end, however, is working far above its normal capacity, 
but it is short, hence the resistance it offers is comparatively 
slight, and gauge 4 registers but little less than gauge 3 and 
the water-main gauge. 

We could go on at great length, showing the action of re¬ 
sistance as applied to water, but we think enough has been 
said to make the meaning clear. 

The pressure under which the water might be would not 
affect the result, except that the higher the pressure the 
greater the amount of resistance which can be overcome, and 
vice versa. 

A pipe of given diameter will carry water up to its capacity 
under any pressure sufficient to move the liquid and less than 
that sufficient to burst the pipe. A pipe of given diameter 
will, however, only convey a certain number of gallons of 
water per minute without excessive friction, regardless of 
whether the pressure be ten pounds or fifty pounds per 
square inch. 

When the point is reached where resistance to flow be¬ 
comes excessive, the normal capactiy of the pipe is said to 
have been reached. 

It is quite true that we may still force a greatly increased 
volume of water through the pipe, but it can only be done 
at the expense of largely increased power consumption. It is 
a costly proceeding to force a water pipe above its normal 
capacity, and the cost increases very rapidly as excess over 
capacity is increased. 

Where it is necessary to convey a certain volume of water 
per minute, and the pipes are overloaded, the practical meth¬ 
od of reducing the resistance attendant upon overload is to 
increase the diameter of the pipe until the desired flow is 


MANAGERS AND PROJECTIONISTS 


63 


obtained with only normal friction loss. We therefore deduce 
the rule that 

Increasing the diameter decreases the friction or resistance 
offered to a given flow, since the water is thus caused to 
move more slowly. 

Another equation enters the matter, however, viz., the 
length of the pipe. Since resistance results largely from 
friction with the walls of the pipe, it follows that the longer 
the pipe the more friction there will be. We have already 
seen that with a given volume of water flowing, as the diam¬ 
eter of the pipe is decreased the friction or resistance is 
increased, and conversely, as the diameter of the pipe is in¬ 
creased the friction or resistance is decreased. 

It is very evident also that with a given flow: 

As the length of the pipe is increased the friction or re¬ 
sistance is increased. Conversely, as the length of the pipe 
is decreased the resistance becomes less. 

We may therefore increase the resistance by (1) increasing 
the flow of water, (2) decreasing the diameter of the pipe, 
(3) increasing the length of the pipe, (4) increasing the in¬ 
terior roughness. 

We may decrease the resistance by (1) decreasing the flow, 
(2) increasing the pipe diameter, (3) decreasing the length of 
the pipe, (4) making the interior pipe walls more smooth. 

We believe the foregoing is simple enough to be readily 
understood. 

What has been said of the action of water flowing through 
pipes is also true with relation to current flowing through or 
over wires. 

If you substitute circuits of wire for the water main, and 
for pipes A, B and C, with volt meters in place of pressure 
gauges, and with lamps, motors or rheostats instead of the 
open pipe ends, you will get precisely the same relative re¬ 
sult in loss of pressure (voltage) when current flow is sent 
through the circuits. 

In considering electrical action the student should clearly 
fix in mind the proposition that the voltage or pressure of 
the current has absolutely nothing whatever to do with the 
size of wire necessary to convey the current. We may con¬ 
vey current at ten thousand or at fifty thousand volts on a 
number 40 wire, which is no larger than a very fine silk 
thread, but the amount of current (amperage) we could con¬ 
vey on such a wire would be very small indeed. 


64 


HANDBOOK OF PROJECTION FOR 


In passing through wires electric current encounters re¬ 
sistance, exactly the same as does water in passing through 
a pipe. A wire of given composition and diameter will con¬ 
vey a certain number of amperes without excessive resist¬ 
ance (electrical friction) precisely the same as a water pipe 
of given diameter and wall roughness will convey a certain 
given number of gallons without undue friction or resistance, 
and the point where resistance in the wire begins to rise 
above normal marks the “capacity” of the wire, exactly as it 
does in the case of the water pipe. Beyond that point the 
friction or resistance becomes excessive, manifesting itself 
in loss of pressure or voltage, which same is dissipated in the 
form of heat. This loss in pressure has been consumed in 
forcing the current against the resistance of the wire, pre¬ 
cisely as was the case in the water pipe. It therefore follows 
that: 

Loading wires beyond their normal capacity is expensive, 
and should be avoided for that reason if for no other, since 
the waste is registered on the meter and you will have to pay 
for it exactly the same as you pay for current used in the 
lamps or motors. 

The loss in electric energy, however, is not the end of the 
matter, because if you attempt to force a wire in the excess 
of its rated capacity as shown by the underwriter’s table 
(see page 70), heat in excess of normal temperature will be 
developed, and if the matter be carried too far (which can 
only be done by overfusing) the wires may get red, or even 
white hot, finally melting and stopping all current flow, and 
perhaps setting fire to the building in the process. Overload¬ 
ing wires is, therefore, not only expensive, but it is also 
dangerous. 

Precisely as was the case with the water pipe, with a given 
current flow the resistance of a wire is decreased as the di¬ 
ameter of the wire is increased, its length made less, or its 
composition changed to one of greater conductivity and is in¬ 
creased as the diameter of the wire is made smaller or its 
length increased, or its composition changed to one of lower 
conductivity. 

Resistance increases... .With increased length of wire; or 

As diameter is decreased; or 
As the temperature is increased 
above normal; or 

As the composition of the wire is 


MANAGERS AND PROJECTIONISTS 


65 


changed to an alloy having lower 
conductivity. 

Resistance decreases... .As length of wire is decreased; or 

As the diameter is increased. 

As the temperature is reduced, if it 
be above normal. 

As the composition of the wire is 
changed to an alloy having higher 
conductivity. 

NOTE.—The difference in conductivity of different metals makes the 
analogy of water and current action more complete, since it corre¬ 
sponds to roughness or smoothness of walls of the water pipe. 


Different metals offer varying resistance to electric current 
as follows, taking the resistance of pure silver and pure cop¬ 
per as 1. 


Copper . 

. 1 

*18% Nickel Silver .. 

....19 

Silver. 

. 1 

Manganin. 

....24 

Aluminum. 

. 1.5 

*30% Nickel Silver... 

....28 

Platinum . 

.6 

♦Advance Wire . 

....28 

Norway Steel. 

. 7 

♦Climax Wire . 

....50 

Soft Steel. 

.8 

♦Nichrome . 

....66 

♦Ferro Nickel . 

.17 




NOTE.—The Driver-Harris Company, manufacturers of resistance 
wires, are authority for these figures. We know of no more reliable 
source for information of this kind. Star (*) indicates Driver-Harris 
products. 

In the foregoing table the figures refer to the amount of 
resistance each metal has, as compared to that of pure, an¬ 
nealed copper. For instance, platinum has 6 and climax wire 
50 times the resistance of pure, annealed copper. 

We have selected for a part of this table metals and com¬ 
positions in very general use for resistance purposes. It will, 
of course, be understood that the figures given in the tables 
are based on metals and alloys of a certain standard purity, 
but inasmuch as the degree of purity will, in the very nature 
of things vary, the relative resistance will vary, accordingly, 
though the variation should not be very great. 

RESISTANCE AND TEMPERATURES.— In the case of 
all metals used for electrical work resistance increases as 
temperature increases. This holds true so far as concerns any 
and everything used for the purpose of conducting the electric 
current, except carbon. In the case of carbon the rule is 
reversed and resistance decreases with increase in tempera¬ 
ture. This is true to such an extent that the carbon filament 















66 


HANDBOOK OF PROJECTION FOR 


of an incandescent lamp offers about twice the resistance 
when cold that it does when the lamp is burning at normal 
capacity. 

It might also be remarked that as a general proposition the 
resistance of liquids and of insulating materials becomes less 
as their temperature is increased. 

TEMPERATURE CO-EFFICIENT.— The resistance of 
metallic conductors not being constant at all temperatures, 
but increasing with rise of temperature, and vice versa, it 
becomes necessary that the student understand the law gov¬ 
erning this matter. 

The increase or decrease of resistance of metals to electric 
current is directly proportional to increase or decrease of 
temperature. 

NORMAL TEMPERATURE. —In figuring such matters all 
calculations are based on normal temperature, which is 75 
degrees Fahrenheit or 24 degrees Centigrade. 

The factor which enables us to calculate the resistance of 
metals with relation to temperature is termed the ‘‘tempera¬ 
ture co-efficient.” In all properly constructed tables of re¬ 
sistance wire the resistance per mil foot of the material is 
given at normal temperature, and the resistance at'this stan¬ 
dard temperature forms the basis of calculation of increased 
or decreased resistance by reason of temperature change. 
The figure given for temperature co-efficient is the fraction 
of an ohm change in resistance for each degree of change 
change in temperature. This co-efficient must be multiplied 
by the number of degrees of temperature change from the 
normal and the result added to or subtracted from the resist¬ 
ance at normal temperature, according to whether the ma¬ 
terial increases in resistance with heat, as in the case of metal, 
or decreases with heat as in the case of carbon, liquids or 
insulating material. 

For example, let us assume the temperature co-efficient of 
a material to be .001, and that its resistance at normal (75 
degrees F.) is 10 ohms per mil foot. What will be its resist¬ 
ance per mil foot at 175 degrees? Subtracting 75 (normal 
temperature in degrees) from 175 (working temperature) we 
find the difference to be 100 degrees, and since resistance in¬ 
creases .001 of an ohm for each degree of increased tempera¬ 
ture, for 100 degrees increase of temperature the increase of 
resistance would be .001 x 100 = .1 of an ohm. We now mul¬ 
tiply the resistance at normal (10 ohms) by the fractional 
increase .1, which gives us the actual total increase of 10 x .1 


MANAGERS AND PROJECTIONISTS 


67 


— 1 ohm, so that the resistance of 175 degrees F. will be 10 
ohms + 1 ohm = 11 ohms. 

It is not our intent or purpose to do anything more than 
show the projectionist how the temperature co-efficient oper¬ 
ates. It is not likely he will have occasion to actually use 
it in practice, but it is nevertheless necessary that he under¬ 
stand the principles upon which such things operate. Those 
who desire further information along these lines can secure 
from their public library books treating on resistance 
materials. 

PROPERTIES OF CONDUCTORS.— Ordinarily electric 
conductors are selected with one of two ends in view. In one 
case low resistance, tensile strength, ductility and cost are 
the ruling factors. In the other case a comparatively high 
and non-fluctuating resistance is the important item. 

In the first instance conductors for current distribution is 
what is wanted, and it is by reason of the fact that copper 
more nearly combines the four above named important factors 
, than does any other metal that it has been selected as the 
standard electrical conductor. 

In the second instance, a material to offer resistance is the 
thing desired, rheostatic resistance forming an integral part 
of electric circuits under some conditions. 

PROPERTIES OF RESISTANCE METALS.— The materi¬ 
als now most generally used for rheostatic resistance in pro¬ 
jection arc circuits are either cast iron, made up in grid form, 
or some one of the nickel steel resistance wires. It is very 
difficult, not to say impossible, to secure reliable data con¬ 
cerning the properties of cast iron, but it nevertheless forms 
an excellent and cheap resistance medium where the tem¬ 
perature co-efficient may be subject to some variation, and 
where a large difference between resistance at normal and 
resistance at high temperature is not of great importance. 
The resistance per mil foot is 64,3 ohms at normal. Climax 
resistance wire made by the Driver Harris Company, Harri¬ 
son, New Jersey, has a resistance per mil foot of 500 ohms 
at normal. Its temperature co-efficient is .000543. Climax 
wire is a nickel steel alloy and a most excellent material for 
rheostat coils. 

Eighteen per cent nickel silver is a composition containing 
18 per cent of nickel. Its resistance varies somewhat with 
different lots. Its mil-foot resistance runs from 170 to 180 
at normal. Its temperature co-efficient is .00015 per degree 
F. Ferro nickel has a mil-foot resistance of 170 ohms at 


68 


HANDBOOK OF PROJECTION FOR 


normal; temperature co-efficient .00115 per degree F. 
Niehrome, also a Driver Harris product, is a practically non- 
corrosive alloy having a melting temperature of about two 
thousand six hundred degrees F. Niehrome is designed for 
use where high temperatures are the rule, as in heating coils, 
etc. Its mil-foot resistance is 660 ohms, and its temperature 
co-efficient point .000095 per degree F. 

Advance wire, a Driver Harris product, is a copper-nickel 
alloy containing no zinc. It is claimed to be constant in its 
resistance under all conditions of service, hence it has no tem¬ 
perature co-efficient. Its mil-foot resistance is 294 ohms. It 
is particularly recommended for electrical installations where 
resistance is subjected to repeated heating and cooling. 

We are indebted for the figures contained in the foregoing 
to the Driver Harris Company, than whom we know of no 
better authority from which to secure reliable data concerning 
resistance materials. Our intention in dealing with this mat¬ 
ter has been merely to give our readers some understanding 
of how temperature affects resistance, and how the resistance 
of a material may be calculated with accuracy for any tem¬ 
perature, providing its temperature co-efficient and its resist¬ 
ance at normal be known; also to advise projectionists and 
theatre managers of at least one source from whence reliable 
resistance materials may be had in case of emergney, and the 
names and peculiar qualities of the various metals obtainable 
from this source. 

LOSS THROUGH RESISTANCE.— It is essential to intelli¬ 
gent, efficient work that the projectionist be able to figure 
the resistance of copper circuits. One of the very first duties 
of the up-to-date, progressive projectionist upon assuming 
charge of a projection room would be to determine whether 
or not the projection room circuits, including its feed wires 
are of sufficient size to operate efficiently and economically. 

As has already been pointed out, the overcoming of resist¬ 
ance consumes voltage, and since all wires offer resistance to 
current flow, voltage will be consumed in (a) proportion to 
the size of the wire, (b) the length of the wire, (c) the tem¬ 
perature of the wire, (d) the composition of the wire, all 
these various factors interlocking with one another. 

Up to a certain point the resistance of a wire remains con¬ 
stant, without change. By this we mean that the resistance 
offered to one ampere or to ten amperes will be identical, but 
when the load becomes such that the temperature of the wire 
rises above normal then its resistance also begins to rise, with 
consequent loss in voltage, or power, which loss will be reg- 


MANAGERS AND PROJECTIONISTS 


69 


istered on the watt-meter. The voltage consumed through 
excessive resistance caused by overloading the wire repre¬ 
sents waste. 

HOW MUCH RESISTANCE.— Broadly speaking, the 

amount of resistance allowable in an electric circuit is: 

For the transmisssion of any given amperage the most 
economical condition is one where the line resistance is such 
that the value of the energy wasted in heat in overcoming 
the resistance of the line will be equal to the interest per 
annum on the original cost of the wires of the circuit plus 
the cost of installation. 

This may be adopted as a safe guide. In practice it means 
that if, for instance, the projection room feed wires are offer¬ 
ing sufficient resistance to cause voltage drop representing 
enough waste energy to more than pay interest on the cost 
of new conductors of larger size, then it will be true economy 
to install the new conductors. 

Under “Figuring Voltage Drop” our readers will be in¬ 
structed how to determine the voltage drop and loss in any 
given circuit, so that they may apply the foregoing in prac¬ 
tice : 

WIRE CAPACITIES.— The National Board of Fire Un¬ 
derwriters, whose ruling must be followed in matters of this 
kind, else insurance cannot be had on the building, has adopt¬ 
ed the amperage rating recommended by the American Insti¬ 
tute of Electrical Engineers. This rating is given in wire 
capacity table No. 1, which determines the number of am¬ 
peres which any ordinary commercial copper electrical con¬ 
ductor may be allowed to carry. In the wire capacity table 
“B & S” means “Browne & Sharpe” wire gauge, which is the 
standard in this country. It is also known as the “American 
Standard” wire gauge. For reasons why rubber covered 
insulation wires have a lower amperage rating than other 
insulations see page 83. i 

Table No. 2 may be used by the projectionist for figuring 
the actual resistance, in ohms, of his various copper circuits, j 
For instance, if the projection room feed circuit has a total j 
length of 75 feet, and is of No. 5 copper wire, referring to I 
table 2 we ascertain the fact that No. 5 copper has .3174 of an I 
ohm resistance per one thousand feet, or .0003174 of an ohm 1 
per foot, and since the circuit is 75 feet long, hence has 150 \ 
feet of copper, the total resistance would be found by mul¬ 
tiplying .0003174 by 150. (Continued under table 1A). 


70 HANDBOOK OF PROJECTION FOR 

TABLE NO. 1—COPPER WIRE CAPACITIES. 

[Note: Tables 1 and 1A are taken direct from the “National 
Electrical Code.”] 

Table No. 1. Allowable Carrying Capacities of Wires. 


B. & S. 
Gauge 

Diameter of 
Solid Wires 
in Mils 

Area in 
Circular 

Mils 

Table A 
Rubber 
Insulation 
Amperes 

Table B 
Varnished 
Cloth 
Insulation 
Amperes 

Table C 
Other 
Insulation 
Amperes 

18 

40.3 

1,624 

3 


5 

10 

50.8 

2,583 

6 


10 

14 

04.1 

4,107 

15 

18 

20 

12 

SO.8 

6,530 

20 

25 

25 

10 

101.9 

10,380 

25 

30 

30 

8 

128.5 

10,510 

35 

40 

50 

G 

102.0 

20,250 

50 

60 

70 

5 

181.9 

33,100 

55 

65 

80 

4 

204.3 

41,740 

70 

85 

90 

3 

229.4 

52,630 

80 

95 

100 

2 

257.0 

66,370 

90 

110 

125 

1 

289.3 

83,090 

100 

120 

150 

0 

325. 

105,500 

125 

150 

200 

00 

304.8 

133,100 

150 

180 

225 

000 

409.6 

107,800 

175 

210 

275 



200,000 

200 

240 

300 

0000 

460. 

211,000 

225 

270 

325 



250,000 

250 

300 

350 



300,000 

275 

330 

400 



350,000 

300 

300 

450 



400,000 

325 

390 

500 



500,000 

400 

480 

000 



600,000 

450 

540 

680 



700,000 

500 

600 

700 



800,000 

550 

660 

840 



900,000 

000 

720 

920 



1,000,000 

650 

780 

1,000 



1,100.000 

690 

830 

1,080 



1,200,000 

730 

880 

1,150 



1,300,000 

770 

920 

1,220 



1,400,000 

810 

970 

1,290 



1,500,000 

850 

1,020 

1,360 



1,600,000 
1,700,000 
1,800,000 

890 

930 

970 

1,070 

1,120 

1,100 

1,430 

1,490 

1,550 



1,900,000 

1,010 

1,210 

1,010 



2,000,000 

1,050 

1,260 

1,670 


1 Mil one one-thousandth (0.001) of an inch. 


Varnished cloth insulated wires 
used only by special permission. 


smaller than No. 6 may be 


Note: For insulated aluminum allow 84 per cent, of Table 1 
capacity rating-. The Board of Fire Underwriters does not 
recognize anything of less than No. 18 wire and nothing less 
than No. 14 may be used for Interior circuit wires. 


















MANAGERS AND PROJECTIONISTS 

TABLE NO. 1A. 

STANDARDIZED STRANDING 


71 


Strands 

Cable 

Allowable Carrying Capacities 
in Amperes 

No. of 
Strands 

| Mils Dia 

B & S. 
Gauge No. 

Area in 

Cir. Mils 

Outside 

Dia. over 

Copper 

Table A 

Rubber 

Insulation 

Table B 

Varnished 

Cloth 

Insulation 

Table C 

Other 

Insulation 

71 25 

22 

4,490 

.075 

15 

18 

20 

71 

32 

20 

7,150 

.096 

20 

25 

25 

7 40 

18 

11,370 

.120 

25 

30 

35 

7 

51 

16 

18,080 

.153 

35 

40 

50 

7 

64 

14 

28,740 

.192 

50 

60 

70 

7 81 

12 

45,710 

.253 

70 

85 

90 

7 91 

11 

58,000 

.273 

80 

95 

110 

7(102 

10 

72,680 

.306 

99 

110 

130 

19 

64 

14 

78,030 

.320 

100 

120 

150 

19 

72 

13 

98,380 

.360 

125 

150 

175 

19 81 

12 

124,900 ' 

.405 

150 

180 

210 

19( 91 

11 

157,300 

.455 

175 

210 

250 

19 107 

* 

217,500 

.540 

225 

270 

325 

19/114 

9 

248,700 

.570 

250 

300 

350 

37 91 

11 

306,400 

.637 

275 

330 

400 

37/ 97 

* 

347,500 

.679 

300 

360 

450 

37/102 

10 

381,200 

.714 

325 

390 

500 

37/116 

* 

484,300 

.798 

400 

480 . 

600 

61/102 

10 

633,300 

.918 

475 

565 

700 

61/107 

* 

698,000 

.963 

500 

600 

750 

61/114 

9 

788,500 

1.030 

550 

660 

825 

61/121 

* 

893,100 

1.090 

600 

720 

900 

61/128 

8 

1,007,000 

1.150 

650 

780 

1000 

91/114 

9 

1,191,000 

1.250 

725 

870 

1125 

91/128 

8 

1,502,000 

1.410 

850 

1020 

1350 

127/114 

9 

1,660,000 

1.480 

900 

1100 

1460 

127/128 

8 

2,097,000 

1.660 ! 

1100 

1300 

1700 


*These individual strands are odd sizes not listed in the American or B. & S. 
Wire Tables. 


Having this data in hand we have only to divide the current 
in amperes by the resistance of the circuit in ohms to get the 
voltage drop. 

Tables 1 and 1A are both correct for any number of 
amperes up to the capacity of the wire, or, in other words, 
until the load becomes great enough to cause a distinct rise 
in temperature. For instance: If you propose to carry only 5 
amperes on a No. 5 wire you would have exactly the same 
total resistance you would have if you carried 50. 

Theoretically this is not strictly true, since there is a rise 
in temperature with any increase in current, but it is true 
in practice, nevertheless, by reason of the fact that with any 
load less than the wire’s capacity the temperature rise is too 
slight to have appreciable effect. 

























72 


HANDBOOK OF PROJECTION FOR 


i 

i 

9 


i 

J 


i 


\ 

I 

« 

0 

t 

I 


For the convenience of our readers we append hereto table 
No. 2, which gives the resistance of copper wire at normal 
temperature. 

TABLE NO. 2 

RESISTANCE OF COPPER WIRE. 


QJ . 

tc O 

Resistance at 75° 

F., International Units 

s z 

Oco 

Ohms 

Ohms 

Feet 

• 

a^ 

per 

1000 Feet 

per 

Mile 

per 

Ohm 

Ohms per Lb. 

0000 

0.04964 

0.2621 

20147. 

0.00007758 

ooo 

0.06261 

0.3306 

15972. 

0.0001234 

00 

0.07804 

0.4168 

12668. 

0.0001962 

0 

0.09945 

0.5251 

10055. 

0.0903114 

1 

0.1255 

0.6627 

7968. 

0.0004960 

2 

0.1583 

0.8360 

6316. 

0.0007894 

3 

0.1966 

1.054 

5010. 

0.001254 

4 

0.2516 

1.329 

3974. 

0.001994 

5 

0.3174 

1.676 

3150. 

0.003173 

6 

0.4002 

2.113 

2499. 

0.005043 

7 

0.5044 

2.663 

1982. 

0.008013 

8 

* 0.6361 

3.358 

1572. 

0.01274 

9 

0.8026 

4.238 

12*6. 

0.02029 

10 

1.011 

5.340 

988.8 

0.03220 

11 

1.277 

6,743 

783.1 

0.05135 

12 

1.609 

8.496 

621.5 

0.08154 

13 

2.026 

10.70 

493.6 

0.1293 

14 

2.556 

13.50 

391.2 

0.2058 

15 

3.221 

17.01 

310.4 

0.3268 

16 

4.070 

21.49 

245.7 

0.5216 

17 

5.118 

27.02 

195.4 

0.8249 

18 

6.466 

34.14 

154.6 

1.317 

19 

8.151 

43.04 

122.7 

2.092 

20 

10.26 

54.15 

97.51 

3.312 

21 

12.93 

68.26 

77.35 

5.263 

22 

16.41 

86.62 

60.95 

8.476 

23 

20.56 

108.6 

48.63 

13.32 

24 

26.00 

137.3 

38.47 

21.28 

25 

32.78 

173.1 

30.51 

33.84 

26 

41.54 

219.4 

24.07 

54.35 

27 

52.09 

275.0 

19.20 

85.44 

28 

66.17 

349.4 

15.11 

137.9 

29 

82.27 

434.4 

12.15 

213.1 

30 

105.1 

554.7 

9.519 

347.6 

31 

131.7 

695.4 

7.592 

546.3 

32 

166.2 

877.4 

6.018 

869.6 

33 

209.5 

1106. 

4.772 

1383. 

34 

264.6 

1397. 

3.779 

2205. 

35 

333.7 

1762. 

2.996 

3507. 

36 

420.1 

2218. 

2.380 

5558. 

37 

38 

530.4 

2801. 

1.885 

8860. 

669.9 

3537. 

1.493 

14131. 

39 

843.0 

4451. 

1.186 

22378. 

40 

1065. 

5625. 

0.9387 

35734. 



















MANAGERS AND PROJECTIONISTS 


73 


When figuring copper wire resistance, still another equation 
enters, however, and a very important one, too, viz., drop in 
voltage. 

MIL-FOOT STANDARD OF RESISTANCE.— The figur¬ 
ing of the resistance of a wire of any size or length is a sim¬ 
ple matter, providing the standard of resistance for that par¬ 
ticular material be known. 

The accepted standard of resistance is the resistance of a j. 
wire one circular mil in cross-section (one one-thousandth of * 
an inch in diameter) and one foot in length, made of the I 
same material as the wire it is purposed to measure. This is | 
what is known as the “Mil-foot standard of resistance.” The ^ 
resistance of such a wire, when made of ordinary commercial * 
copper, is given by standard text books as 10.5 ohms. That | 
is to say, a wire one foot in length and one one-thousandth * 
of an inch in diameter (one mil area of cross-section), made | 
of ordinary commercial copper, at normal temperature (75° F. * 
or 24° C.), will have a resistance of 10.5 ohms. 

FIGURING RESISTANCE OF COPPER CIRCUITS —And f 

now let us proceed to apply the foot-mil standard in measur- j* 
ing wires. Suppose you have a wire 400 feet in length and 1 
1 circular mil cross section (1/1000 of an inch in diameter), 
made of ordinary commercial copper. It is evident that if 
one foot of such a wire has a resistance of 10.5 ohms, 400 feet 
would have a resistance four hundred times as great, or 
10.5 x 400=4200 ohms. The resistance of a wire of given 
length, however, decreases as its diameter or area of cross- 
section is increased. If our 400-foot wire has a diameter of 
250 mils, it will have a cross-section equal to 250x250=62,500 
C.M., and it follows that its resistance would be equal to the 
resistance of 400 feet of one-mil wire (4,200 ohms) divided by 
the C.M., cross-section of the larger wire (62,500), since it 
would be, in effect, equal to 62,500 wires, each one circular 
mil in cross-section, or one mil in diameter. From this we 
get the rule: 

To find the resistance of a copper wire, multiply its length 
in feet by # 10.5 and divide that product by its area in circular 
mils. 

In measuring circuits, however, it is customary to take the 
one-way length and double the mil-foot standard, thus: mul¬ 
tiply the one-way length of the circuit by 21 (10.5x2=21) and 
divide that product by the area of the wire in the circuit; ex¬ 
pressed* in circular mils. 


74 


HANDBOOK OF PROJECTION FOR 


For example: What is the resistance of a two-wire projec¬ 
tion room feed' circuit 75 feet in length—size of the wire No. 
5? If we were measuring only one 75-foot-long wire we 
would apply the above rule, using 10.5 as the standard of re¬ 
sistance, but as a matter of fact a circuit 75 feet long has 150 
feet of wire, and for convenience’s sake we double the mil-foot 
standard, instead of doubling the wire length. 

In Table 1, page 70, we find that No. 5 wire has a cross- 
section of 33,088 C.M, We then have the problem': 

Length of circuit x 21 75x21 

-=-= .0475 + of an ohm, which is 

C.M. area of wire 33,088 

the resistance of the circuit. This rule is, of course, based on 
the proposition that the wire will not exceed 75 degrees F., 
or 24 degrees C. However, the rise and fall in temperature 
caused by ordinary climatic conditions is not sufficient to 
materially affect the result. In fact, resistance does not begin 
to rise appreciably until the temperature has increased suf¬ 
ficiently to be sensible to the feeling; beyond that point it 
increases very rapidly with the temperature. 

FIGURING VOLTAGE DROP.— We think it advisable to 
provide the accepted formulas for figuring voltage drop, even 
though the projectionist and the theatre manager may only 
have use for them on rare occasions. 

The question of voltage drop is given altogether too little 
consideration in theatres. In the following formulas 

L stands for one-way length of circuit. 

A stands for cross-section in circular mils. 

e stands for voltage drop, in volts. 

E stands for voltage of circuit. 

I stands for current in amperes. 

R stands for resistance in ohms. 

P stands for voltage drop, expressed in percentage. 

Where the length of the circuit, the area of cross-section of 
the wire, together with its mil-foot standard of resistance, is 
known, the ohmic resistance may be calculated according to: 

21 xL 

Formula No. 1: R =- 

A 

in which 21 is a constant equal to twice the resistance of the 
mil-foot standard for copper wire. Twenty-one and the one¬ 
way length of the circuit are used, instead of 10.5 and the 




MANAGERS AND PROJECTIONISTS 


75 


total length of the two wires, merely for the sake of con¬ 
venience. 

Example : What is the resistance of a circuit of No. 6 cop¬ 
per wire haying a one-way length of 200 feet? Using formula 
No. 1, substituting figures we have 

21 x 200 4200 

-=-= .16 of an ohm. 

26,250 26,250 

Formula No. 2 —e = IxR, meaning that voltage drop equals 
amperes multiplied by resistance of the circuit. Example: 
What is the voltage drop of a circuit of copper having .16 
of an ohm resistance and carrying 50 amperes? Substituting 
figures we have : e = 50 x .16, or an 8 volt drop. 

21 x 1 x L 

Formula No. 3: e =-, in volts. Example: What 

A 

is the voltage drop of a copper circuit of No. 6 wire having 
a 200 foot one-way length, carrying 50 amperes? Substitut- 

21 x 50 x 200 

ing figures we have: e = - = 8 volts drop. 

26,250 
21 x 1 x L 

Formula No. 4: A = -, in circular mils. Ex- 

e 

ample: What size of wire (area of cross-section) is necessary 
to give an 8 volt drop in a copper circuit having 200 feet one¬ 
way length, carrying 50 amperes? Substituting figures we 
21 x 50 x 200 

have: A = -= 26,250 circular mils. 

8 

Formula No. 5. When the voltage drop is expressed in 
percentage the following formula may be used to determine 
the area of cross-section of wire necessary to give the de- 
2100 x 1 x L 

sired drop. -= area of cross-section in circular 

ExP 

mils. Example: Suppose you want a circuit having a one¬ 
way length of 60 feet to carry 100 amperes with a 3 per cent, 
voltage drop; voltage of circuit 110. Substituting figures we 
2100 x 100 x 60 

have:--, which equals 38,181 circular mils, and 

110 x 3 

since a No. 5 wire would be too small (see table No. 1) we 









76 


HANDBOOK OF PROJECTION FOR 


would have to use No. 4, which would be a little too large 
and would not give quite the 3 per cent. drop. 

Formula No. 6.—If the power is given in watts, the re¬ 
quired area of cross-section of wire to give a desired voltage 

2100 x W x L 

drop may be figured thus: - equals area of 

P x E 

cross-section in circular mils, W standing for watts, of 
course. 

And now let us apply the foregoing in practice. A two- 
wire projection room feeder supplies 50 amperes at a distance 
of 200 feet from the house switchboard; we will assume that 
a 5 per cent, drop in voltage is allowed, the supply voltage 
being 110. What size wire should be used? Referring to the 
formula we select No. 5, and, substituting figures, the nec¬ 
essary size of wire is found as follows: 

2100 x 50 x 200 

A = -= 38,181 circular mils 

110 x .05 

Turning to our capacity table we find that a No. 5 wire has 
an area of 33,088 C.M. and a No. 4 has 41,740, so that while 
a No. 4 would be largely in excess of the requirements, a 
No. 5 would be too small. 

If this energy were used for ten hours a day for 300 days 
and the cost of the energy were 8 cents per k.w. hours, the 
total yearly cost would be: 

50 x 110 x 300 x .08 

-= $1,320, 

1000 

5 per cent, of which is $66, which latter amount would 
express a yearly loss due to the 5 per cent, drop when 
using 50 amperes at 110 volts, and at a cost of eight cents 
per K.W. Once the nature of the problem is understood it 
is an easy matter to determine the best course of procedure. 
Sixty-six dollars represent 8 per cent, on approximately 
$800, so that if larger conductors can be installed for that 
sum, or less, and the loss thus reduced, it certainly will pay 
to do it, since paying out sixty-six dollars a year for wasted 
electric energy is precisely the same as paying that sum 
out in the form of interest. 

Of course, we have assumed an arbitrary current cost of 
eight cents per K.W. If current is had for less, the figures 
will be changed. We have, we hope, made the nature of the 
problem clear, and having done that must leave it to the 





MANAGERS AND PROJECTIONISTS 


77 


individual projectionist and exhibitor to figure out his own 
problem. 

The data supplied is important, because by its intelligent 
application it will very often be found that much money is 
wasted in the excessive resistance of circuits, which could 
be avoided by installing wires of larger size. It is therefore, 
we repeat, essential that the projectionist and manager have 
a good working knowledge of matters of this sort. 

THE MEASUREMENT OF WIRES.— The area of cross- 
section of electrical conductors of various kinds is measured 
either in square or circular mils, the latter being used for 
round wires and the former for square or rectangular con¬ 
ductors. 

A circle measuring 1/1000 of an inch in diameter is called 
a “circular mil,” the same being commonly abbreviated “C.M.” 

A round wire 1/1000 of an inch in diameter is said to have 
an area of cross-section of one circular mil, “cross-section” 
being the surface of the end of a wire. 

The area of round wires is directly proportioned to the 
square of their diameters, the calculation being made in 
circular mils. 

“Squaring the diameter” means multiplying the diameter 
by itself, thus: if a wire be 10 mils in diameter, then 10 x 10 
= 100 is the square of its diameter, hence the area of its 
cross-section in C.M. 

Let us consider a wire having a diameter of of an inch. 
Since one inch is equal to one thousand thousandths (1000/ 
1000), the-diameter of the wire expressed in thousandths of 
an inch, or mils, would be equal to 1000 4 = 250. A wire 

% of an inch in diameter is, expressed after the electrical 
fashion, 250 mils in diameter, and since the area of cross-sec¬ 
tion of a wire in circular mils is equal to the square of its 
diameter in mils, it follows that our quarter-inch-diameter 
wire would have an area of 250 x 250 = 62,500 circular mils. 

The circular mill area of any round wire may be found 
by measuring its diameter in thousandths of an inch, using 
a micrometer caliper or wire gauge for the purpose and 
multiplying the measurement thus obtained by itself. The 
result will be the C.M. area of the wire. 

The capacity of any round wire may be found by measur¬ 
ing the wire diameter as above set forth, multiplying the 
measurement by itself and comparing the result with “Area 
in C.M.” column in wire capacity table, page 70. 


78 


HANDBOOK OF PROJECTION FOR 


B. & S. WIRE GAUGE.— The accepted standard for wire 
measurement in this country and Canada is the American 
gauge, commonly known as the “Brown & Sharpe” gauge, 
which in practice is dubbed the “B. & S.” gauge. 

This gauge is illustrated in Fig. 7. In using the tool it 
is the slot, and not the round hole which determines the 
size of the wire. In using the gauge select the slot in 
which the wire fits snugly, without binding. A wire gauge 
of this type should have the width of the slot, or in other 



Figure 7. 

words the mil diameter of the wire which fits the slot, 
stamped opposite each slot on one side of the gauge, and 
the number of the wire which fits the slot on the other side. 
For example, opposite the slot in which a No. 16 wire fits 
will be found the No. 51, meaning 51/1000 of an inch, or 51 
mils diameter, the terms thousandths of an inch and mils being 
interchangeable. Note: This is not exactly accurate. The 
precise measurement is 50.0820, but there would not be room 
on the gauge to stamp such long numbers legibly. 

MICROMETER CALIPER. —Wires may also be measured 
with absolute accuracy by means of a micrometer caliper 
such as is illustrated in Fig. 8. 

This tool is, however, expensive; moreover the man un- 









MANAGERS AND PROJECTIONISTS 


79 


accustomed to handling such tools would have difficulty in 
using it. Micrometer calipers made for the use of electri¬ 
cians have the wire size and their equivalent in mils stamped 
thereon. Thus: Looking at Fig. 8, if a wire measures 31.9 
thousandths of an inch in diameter, we see that it is a number 
20 wire. If it measures 162 thousandths of an inch (mils) 
we see that it is a number 6 wire, etc. 

For measuring very small wires, such as the strands of an 
asbestos covered wire (usually a No. 30 or No. 31) the slot 
wire gauge is reliable only in the hands of an expert. If the 
projectionist desires to measure his asbestos covered wire 


Figure 8. 



strands and he has no micrometer caliper, it would be better 
to have a machinist measure a few of the strands with a 
micrometer. Every projectionist should own a wire gauge 
or micrometer caliper. If the former, it should be a good 
gauge, not one of the unreliable catch-penny affairs which 
are worse than nothing at all. The Brown and Sharpe Stand¬ 
ard Wire Gauge for copper wires, illustrated in Fig. 7, is 
thoroughly reliable. It will serve all the purposes of the 
projectionist, except for the accurate measurement of very 
small wires. 


DO IT NOW. 








































80 


HANDBOOK OF PROJECTION FOR 


Insulation 

I NSULATION is for the purpose of confining the electric 
impulse, current or E. M. F. to the wire. Its purpose is 
to prevent electrical contact between wires of opposite 
polarity attached to the same generator. Put in other words, 
the purpose of insulation is to keep the wires from coming into 
electrical contact with each other, or with any object which 
might furnish an electrical path of conductivity to a wire of 
opposite polarity attached to the same dynamo or battery. 
Such a path of conductivity may be supplied by direct contact 
between two wires, by means of both wires coming into con¬ 
tact with a third wire or other object which will conduct elec¬ 
tricity, or y both wires making contact with the ground. 
In short, insulation is to protect the potential of or on a 
wire from escaping to a wire of opposite polarity. 

As has already been shown, various metals offer resistance 
in varying amount to the passage of electric current. It 
is also true that various materials other than metals offer 
a varying resistance to the passage of electric current, and 
while there is no material known which is an absolute non¬ 
conductor—through which the electric current cannot be 
forced if the voltage is raised sufficiently high—still there 
are materials which are considered as being and which 
are treated as non-conductors, because current cannot be 
forced through them by any ordinary commercial voltage. 
These substances are called “insulating materials” and at their 
head stands, in the order named, glass, porcelain and rubber. 

Various natural substances, such as marble and slate, form 
excellent insulating materials for ordinary voltage. Asbestos, 
when dry, is also a very good insulator. Then, too, there are 
various insulating compounds, the composition of some of 
which are trade secrets. In practice these compounds are 
used to saturate some sort of braid or other material which 
after being so saturated is used for weatherproof insula¬ 
tions on wires to be used out of doors or to re-enforce the 
insulation of rubber covered wires. 

R. C. AND WHAT IT IS. —Rubber covered wire consists 
of copper wire which has been coated with tin, upon which 


MANAGERS AND PROJECTIONISTS 


81 


is laid a covering of pure rubber or rubber compound of 
homeogeneous character, over which is placed one or more 
outer coverings of braided cotton which have been soaked 
in a preservative fireproof insulating compound. Where 
copper wire is covered with rubber, or any of the rubber 
compounds, the tinning of the wire is very necessary, since 
the sulphur, universally present in rubber insulation is likely 
to combine with the copper, in which case the wire would in 
a very short time become corroded, and thus either very 
greatly weakened or perhaps entirely destroyed. The tinning 
of the wire prevents this, since because tin will not combine 
with sulphur, the rubber insulation has no effect upon it. 

It is not the purpose of this work to enter into an exhaus¬ 
tive treatise on insulating materials, which subject would 
in itself fill a large volume. Our intent is merely to give the 
projectionist a general understanding of the proposition as 
a whole. Those who wish to study the matter of insulation 
exhaustively should visit their public library and consult 
standard electrical works which deal with insulation. 

The current must be confined to the wires and made to 
pass from positive to negative through the paths provided, 
and through them only, the said paths being motors, in¬ 
candescent lamps, arc lamps, et cetera. The ability of insula¬ 
tion to resist electrical action must increase with increased 
voltage, and its kind or type must vary with the service. 
The insulation known as “weatherproof” may be used 
wherever wires are stretched in an open area, and for out- 
of-door circuits, but for interior work only “rubber covered” 
wires may be used. 

INSULATION RESISTANCE.— Where a test of the wiring 
of a building is required by the Inspection Department the 
wiring must comply with the following requirements: 

The complete installation must have a resistance between 
conductors and between all conductors and the ground (not 
including attachments, sockets, receptacles, etc.) not less than 
that given in the following table: 

Up to 5 amperes.4,000,000 ohms. 


“ 

10 “ . 

. 2 , 000,000 

i < 

« 

25 “ . 

. 800,000 

«< 

tt 

50 “ . 

. 400,000 

< < 

<* 

100 “ . 

. 200,000 

it 


200 “ . 

. 100,000 

it 


400 “ . 

. 50,000 

it 


800 . “ . 

. 25,000 

it 

“ 

1,000 “ . 

. 12,500 

t c 


The test must be made with all cut-outs and safety devices 















82 


HANDBOOK OF PROJECTION FOR 


in place. If the lamp sockets, receptacles, electroliers, etc., are 
also connected only one-half of the resistance specified in the 
the table will be required. 

TYPES OF WEATHER-PROOF INSULATION —There 

are two types of weatherproof wire, viz., weatherproof and 
slow burning weatherproof. The insulation of the slow burn¬ 
ing weatherproof consists of two coatings, one of which is 
fireproof and the other not. The fireproof coating is on the 
outside and comprises about 6/10ths of the total thickness 
of the insulation. The complete covering for size of wire 
from No. 14 to 0000 varies from 3/64ths to 5/64ths of an inch. 

Fireproof insulation is not as susceptible to the action of 
heat as is ordinary weatherproof, which latter softens quickly 
under its influence. Fireproof insulation is not, however, 
suitable for outside work, being intended for interior work 
in warm, dry places, such as shops and factories. When so 
used, underneath it, next to the wire there must be a coating 
of rubber. 

Slow burning insulation, which is still more fireproof than 
the slow burning weatherproof, is intended to be used in 
very hot places, where ordinary insulation would soon perish. 
Weatherproof insulation should consist of at least three 
layers of braid, each thoroughly saturated with a dense, 
moisture-proof compound, applied in such manner as to 
drive out any atmospheric moisture contained in the material, 
thus securing a covering which will not only have high 
insulating power, but which also will to a great extent be 
waterproof. The outer covering of this insulation is pressed 
down to a hard, dense surface. 

Wire thus insulated is intended for use out-of-doors where 
there will be moisture and where fireproof qualities are not 
necessary. In general, weatherproof wires may be used 
only where the supports on which the wire is mounted are of 
insulating material and are depended upon for insulation, 
the covering being regarded merely as a precaution against 
accidental contact with other wires, or other objects. 

In addition to these there is a varnished cloth insulation 
which may only be used in places free from moisture. 

From the foregoing we may understand that the principal 
difference between rubber cover and other insulation lies 
in the fact that rubber cover insulation may be depended 
upon to do the actual insulating, whereas the other must 
depend, at least to a considerable extent, on the wire support 
itself for insulation. Rubber covered wire may be used any- 


MANAGERS AND PROJECTIONISTS 


83 


where weatherproof would be allowable, but not in places 
where slow burning weatherproof or fireproof insulation 
would be required. 

Rubber covered wire of size No. 8 or less need have but one 
layer of braid and one braid wire No. 8 or less in size may 
be used in conduit. R. C. wire of greater size than No. 8 must 
have either two layers of braided material or a layer of 
tape with the rubber and a layer of braided material out¬ 
side. 

The reason rubber covered wire is rated at lower capacity 
than weatherproof is that rubber is easily and quickly injured 
by even a moderate amount of heat. Remembering that the 
passage of the current through wire generates heat in over¬ 
coming resistance, it will be readily seen that where an in¬ 
sulation which is easily injured by heat is used a wide margin 
of safety must be maintained. 

WARNING.—R. C. is the only insulation permissible for use 
in conduit. 


KNOWLEDGE IS POWER. 



84 


HANDBOOK OF PROJECTION FOR 


Wire Systems 

T WO-WIRE SYSTEM. —The projectionist of today is not 
likely to come in contact with any except the two and 
three wire systems. It is true that the “Series Arc Sys¬ 
tem” is still in use for street lighting, but it may be disposed 
of, so far as the purposes of this work be concerned, with the 
remark that it is not practical to connect a projection arc 
lamp to it. Should the projectionist encounter a series arc 
lighting system the only thing he can do is to let it severely 
alone. Should he attempt to connect a projection lamp to it, 
he will most likely put the whole system out of business, and 
may get himself severely hurt, or even killed. 

The “Multiple Arc” or “Two Wire System” is illustrated in 



Fig. 9, in which the heavy lines represent street mains coming 
directly from the power house, circuits D—D branch mains 
feeding a district or a street, and the thin lines E—E—E house, 
store, factory, theatre circuits, etc. We see a projection lamp 
attached to one of these latter circuits, all switches, fuses, 
etc., being omitted. 

Assuming the system to be charged with ordinary commer¬ 
cial voltage, we may attach a projection lamp to the wires at 





















MANAGERS AND PROJECTIONISTS 


85 


any desired point, provided (a) the wires, switches, fuses, etc., 
be large enough to carrj>- the current necessary for the arc, 
plus whatever else they will have to carry, without over¬ 
load; (b) provided sufficient resistance be connected in series 
with the lamp to supply required number of amperes. 

In the foregoing, by “commercial voltage” we mean anything 
up to, say, 250 volts, though it is practical to handle even as 
much as 500 volts by means of rheostatic resistance, and that 
is as high as the voltage will ever reach on any D. C. cir¬ 
cuit. If the current be A. C., then a projection lamp may be 
attached at any desired point, provided the same -precautions 
be taken as before named for D. C.; but if the voltage be in 
excess of, say, 110, you then should only attach your projec¬ 
tion lamp to the secondary circuit of a transformer, which will 
automatically reduce the voltage line to a pressure suitable 
for use. This latter will be explained in detail under the 
heading of “Transformers,” page 544. 

In this connection, let it be remarked that the traveling pro¬ 
jectionist will do well to procure a copy of McGraw’s Elec¬ 
trical Directory, which is for sale by the McGraw Publishing 
Co., 239 West Thirty-ninth street, New York City. This book 
is issued yearly. It gives the necessary particulars concerning 
every electric generating plant in the country, such as the kind 
of current, voltage of the system, its capacity, etc. 

We shall not remark further upon the two-wire system be¬ 
cause it is in effect also dealt with in the three-wire system, 
which is the one most commonly encountered and which is 
to a very large extent merely the joining of two two-wire 
systems; therefore, if we went into extended detail on the 
two-wire system, much of what we would have to say on the 
three-wire system would be in the nature of a repetition, and 
there are too many things demanding attention to waste 
space. 

THREE-WIRE SYSTEM. —The most widely used system 
for the distribution of light and power is what is known as 
the “three-wire system,” illustrated in Fig. 10. The basic prin¬ 
ciple upon which this system operates is the fact that if two 
dynamos of the same characteristics be connected in series 
—the positive pole of one machine electrically connected to 
the negative pole of the other—the voltage between the posi¬ 
tive and negative terminals of the combination thus effected, 
or in other w'ords, the potential difference between the outer 
poles or terminals of the two machines, will be double that 
of either dynamo measured separately. 


86 


HANDBOOK OF PROJECTION FOR 


If each dynamo be a 110-volt generator, then the pressure 
between the outer terminals and the wires connected to them 
(wires E and F) will be 220 volts, though if at the same time 
the voltage be taken across the positive and negative terminal 
of either dynamo separately (between wires E and D or D»and 
F), the reading would only be 110. It therefore follows that 
if a wire be attached to the outer terminals of two generators, 
as per wires E—F, Fig. 10, in which circles A and B represent 
110-volt dynamos, and the other two terminals be joined by 
wire C, as shown, the voltage between these two wires will 
be double-the voltage of either machine separately. If a 



third wire, D, be attached to connecting wire C, the voltage 
reading between either wires E—D or D—F, would be half 
that between wires E and F. In such a combination the center 
wire D is called the “neutral.” The combination is such that 
current from either dynamo may be used without in any way 
affecting the other dynamo. Two outside wires E—F, are 
known respectively as the “true” negative and “true” positive 
of the combination, but 

Neutral wire D is negative to dynamo A and positive to dy¬ 
namo B, so that as a matter of fact it is both positive and 
negative, and when using current from either dynamo sep¬ 
arately it will be either a positive, or a negative wire 
according to from which dynamo the current is taken. 

If we connect a lamp or motor to wires E and D, then wire D 
will be just as truly negative as though dynamo B did not 






















MANAGERS AND PROJECTIONISTS 


87 


exist. If we connect to wires D and F, then wire D will be 
just as truly positive as though dynamo A did not exist. 

G—H and I are voltmeters. Voltmeters G and H will each 
register 110 volts and voltmeter I will register 220 volts. 

Put in another way, in the three-wire system we have what 
is in effect two complete two-wire systems joined together in 
such way that they may either be used separately at 110 volts, 
or jointly at 220 volts. The reason for such a combination 
is that it is economical in installation cost and maintenance, 
since the same electrical energy can be transmitted over a 
three-wire system that could be conveyed over two separate 
two-wire systems having wires of equal size; also, there is the 
added advantage of being able to use 110 volt incandescent 
lamps (which are very much better than 220 volt lamps) and 
either 110 or 220 volt motors. 

Assuming the system shown in Fig. 10 to be in operation, 
its electrical action will be as follows: First let us switch 
off lamps J, L and N, leaving only lamps K and M burning. 
Assuming the lamps to consume 55 watts each, the amperage 
passing through any one of them when burning alone on 110 
volts pressure would be 55 110 = .5 of an ampere; also, 
the amperage passing through two such lamps when burning 
in series at 220 volts would be 110 220 = .5 of an ampere, 

each lamp consuming 55 watts or 110 watts in all. 

A peculiarity of the three-wire system is that lamps or 
motors connected to opposite sides will always, when possible, 
operate in series, the current always seeking the true negative 
rather than the neutral wire. 

It therefore follows that-with only lamps K and M burning, 
they would burn “in series” at 220 volts’ pressure, hence Yz 
ampere of current would pass out from generator A and 
along wire E to lamp K. The current would pass through 
lamp K to the neutral wire, 110 volts of its E. M. F. being con¬ 
sumed in forcing the current through the resistance of the 
lamp filament, along the neutral wire to lamp M, through 
lamp M and back to generator B along wire F, the true 
negative of the combination. Under this condition no current 
at all would pass over the neutral wire, except between the 
points at which lamps K and M are connected to it. 

Let us now switch on lamps L and- N, whereupon instantly 
one ampere of current will follow along wire E up to the 
point where lamp K is connected to it. At this point the 
ampere will divide, one-half going through lamps K and M 
the other half continuing on and passing through lamp s L 


88 


HANDBOOK OF PROJECTION FOR 


and N, so that we now have one ampere flowing on fhe true 
negative between the generator and the point where lamp M 
is connected to wire F. The combination is now producing 
one ampere of current under 220 volts’ pressure and is what 
the electrician would call “perfectly balanced.” 

BALANCED SYSTEM. —A three-wire system is said to be 
“balanced” when lamps or motors consuming precisely the 
same amount of current are attached between the neutral 
and either of the outside wires. In other words, when each 
“side” is carrying exactly the same load, under which con¬ 
dition everything operates in series and no current flows on 
the neutral’between the generator and the first current using 
device attached to it. So long as this condition be maintained, 
the power-house neutral fuse could be removed without in 
any way affecting the system. 

From the power-house viewpoint a perfectly balanced three- 
wire system is highly desirable. This ideal condition is, how¬ 
ever, seldom or never realized in practice. There is prac¬ 
tically always more load on one side than on the other, and 
amperage equal to the difference between the load on the 
two sides flows back to the generator on the neutral wire. 
If the system is a 110-220 volt one, and 26,400 watts are being 
used on one side and 24,200 on the other, then 26,400 minus 
24,200 equal 2,200 -s- 110 == 20 amperes will flow back to the 
generator on the neutral wire. The practical effect of this 
would be that one generator would produce 20 amperes 
(2,200 watts) more than the other. 

For this reason officials of heavily loaded three-wire systems 
often object to projection arcs being connected to one side of 
the system. Both the dynamos are working close to capacity, 
and if a projection arc, which is in the nature of an inter¬ 
mittent load of considerable amount, be hitched to one side, 
that amount of load is thrown on one dynamo and the system 
is thus intermittently unbalanced. 

However, if the projectionist is reducing his voltage with a 
rheostat there would be no advantage in connecting the pro¬ 
jection arc across the outside wires, since although the 
amperage would remain the same, an amount of energy equal 
in watts to an additional arc of equal capacity would be con¬ 
sumed in the resistance necessary to take care of the extra 
110 volts. Thus, instead of having one dynamo intermittently 
loaded with a projection arc, both generators would carry 
an additional load equal in watts to the arc amperage times 
110 . 


MANAGERS AND PROJECTIONISTS 


89 


If, however, an economizer, a mercury arc rectifier or a 
motor generator set be used for voltage reduction, then there 
is large advantage in connecting to the two outer wires, since 
there would then be no unbalancing effect and the total 
energy taken from the lines would be practically the same as 
when connected to one side at 110 volts. It may be accepted 
as fact that, 

If the line voltage be reduced by means of a rheostat, the 
power company can have no reasonable excuse for compelling 
you to attach your projection arc to the outside wires of a 
three-wire system. Such a connection would cost exactly 
twice as much for electrical energy to operate the arc as it 
would cost if you were connected to one side at 110 volts, and 
places double the load on the system. 

But to return to the consideration of Fig. 10, we have seen 
that with lamps K, L, M and N burning the system is balanced 
and no current flows back to the generator over neutral 
wire D. Let us now turn on lamp J in addition to lamps K, 
L, M and N. This will cause \ l / 2 amperes to be generated, 
which will flow out on wire E to the point where lamp J is 
connected, whereupon it will divide up as shown, ampere 
passing through lamp J, through lamp K and ^2 through 
lamp L. Between wires D and F ]/ 2 ampere will flow through 
lamp N and y 2 through lamp M, but there is no lamp to 
balance lamp J, therefore the current flowing through it must 
return to the generator over neutral wire C. Hence we now 



Figure 11. 



































90 


HANDBOOK OF PROJECTION FOR 


have the system unbalanced by ampere, with 1J4, 1 
ampere flowing respectively in wires E, D and F between the 
lamps and the generators, and generator A producing Yz 
ampere more of current than generator B. 

Insofar as current flow be concerned that is the way the 
three-wire system operates, but there are some points in con¬ 
nection with it which are very puzzling to the novice and 
more or less so to some more experienced men. 

Fig. 11 is the diagrammatic representation of several house 
circuits fed by a three-wire service circuit, each wire of which 
is fused at 60 amperes. Between the neutral (central) wire and 
the upper wire, circuits A, B and C are connected, each of 
which is connected to apparatus using just 10 amperes. 
Between the neutral and the lower wire circuits D, E and F 
are connected the first two using 10 amperes each. Circuit F 
is idle. 

Question: Would it be possible to attach a 25-ampere pro¬ 
jection arc to circuit F, when the three main wires are only 
fused to 60 amperes and the circuit already loaded as shown? 

The novice will probably answer, “No, the circuits are 
already using 50 amperes, and the addition of a 25-ampere arc 
would overload the fuses.” The novice would, however, be in 
error, because the circuits are not using 50 amperes, but only 
30, 10 of which are handled individually by the generator at¬ 
tached between the neutral and the upper wire. Circuits A, 
B, D and E will burn in series, as has already been explained, 
so that instead of 40 amperes at 110 volts, the lamps or motors 
on circuits A, B, D and E will work in series on 220, and only 
a total of 20 amperes will flow. 

Circuit C will use 10 amperes at 110 volts, just as though 
wire 3 did not exist, as long as circuit F is idle. This will 
have the effect of causing the upper wire to carry 30, the lower 
20 and the neutral to carry 10 amperes, so that the upper fuse 
will carry 30 amperes, the neutral fuse 10 amperes and the 
lower fuse 20 amperes. Under that condition the system is 
unbalanced 10 amperes, and the generator attached to the 
neutral and upper wire is carrying that much more load than 
is the generator attached to the neutral and lower wire. 

Suppose we now connect a 25-ampere projection arc to 
circuit F. Circuit C now burns in series with circuit F to the 
extent of 10 amperes, but 15 amperes of the 25 must come 
from the generators over neutral wire, so that we now have 
the following condition: The upper fuse carries 30, the center 
fuse 15 and the lower fuse 45 amperes, and the generator 


MANAGERS AND PROJECTIONISTS 91 

attached to the neutral, and lower wires is generating 15 
amperes more than its mate. 

We therefore see that instead of being overloaded the fuses 
would actually be too large to properly protect the apparatus, 
were it not for the individual circuit fuses. To be fused 
absolutely right for the protection of the apparatus, we should 
now have a 30-ampere fuse in the upper, a 15-ampere fuse in 
the center and a 45-ampere fuse in the lower contact, though 
this is never done in practice, the fuses shown being intended 
to protect the main wires, the capacity of which would pre¬ 
sumably be 60 amperes. The apparatus and smaller wires are 
protected by individual circuit fuses not shown in the diagram. 

If your theatre is fed by a three-wire system it is important 
that the two sides be balanced as nearly as possible. If the 
theatre system is unbalanced and the neutral fuse should blow, 
then the effect is that of forcing the lights attached to one 
side above candle power, while those on the other side would 
burn below candle power. 

It is always possible to tell exactly how much, if any, the 
load is unbalanced by connecting an ammeter into the neutral 
house feeder. 

THREE-WIRE SYSTEM WIRE SIZES.— To figure wire 
sizes for three-wire circuits, proceed the same as for the 
ordinary two-wire system, considering only the two outside 
wires. Having determined the necessary capacity of the two 
outside wires, make the center wire the same size. 


MR. EMPLOYER, YOU CANNOT 
REASONABLY EXPECT HIGH- 
CLASS WORK FROM YOUR MEN 
UNLESS YOU ENCOURAGE IT. 
THE UNION SCALE IS MERELY A 
MINIMUM YOU ARE EXPECTED 
TO PAY THE POOREST MEN. IF 
YOU WANT SOMETHING BETTER 
YOU SHOULD BE WILLING TO 
PAY FOR IT. 



92 


HANDBOOK OF PROJECTION FOR 


Switches 

I T is essential that the projectionist be able to recognize 
the various types of switches met with in theatre work, 
also that he understand certain things with regard to their 
installation and proper care. 

The various types of knife switches ordinarily encountered 
in theatre work are the double pole single throw (D. P. S. T.) 
double pole double throw (D. P. D. T.) three pole single throw 
(T. P. S. T.) and three pole double throw (T. P. D. T.). 

In Fig. 12 we see 
at the top a S. P. 
S. T. knife switch 
mounted on a slate 
insulating base, slate 
being an insulating 
material for ordi¬ 
nary commercial 
voltages. A is the 
blade, B the handle, 
E E the terminals, 
D the hinge and C 
the contact. Im¬ 
portant points in the 
care of switches are 
(a) that hinge D be 
kept set up snugly, the proper pressure being that which 
will cause the blades to remain in any position placed. If the 
switch is held upright, and when the blade is pulled out it 
falls down of its own weight making contact with C, then 
hinge D is too loose and should be tightened. The next im¬ 
portant point is that contact C be so adjusted that there will be 
good, firm electrical contact between the blade and the con¬ 
tact clips C when the switch is closed. It is amazing how care¬ 
less some projectionists are about such details. We have 
many times, in high class projection rooms, found switches 
loose and wobbly in their hinges, or making such poor contact 
at C that considerable heat was generated. 

SWITCH INSTALLATION.— In the installation of knife 
switches, such as shown in Figs. 12 and 13, it is important 






MANAGERS AND PROJECTIONISTS 


93 


that the switch be so placed that the tendency will not be for 
the switch to close itself by gravity. This means that the 
upper switch in Fig. 12 should, if mounted on a wall, always 
be placed either sidewise or with its handle up. 

Switches often have fuses mounted on their base. In Fig. 
12 the lower illustration shows an S. P. S. T.. knife switch 
with fuse contact at the left, these contacts being designed to 
take what is known as the “knife blade” cartridge fuse. The 
fuses are not in place. 



Figure 13. 






94 


HANDBOOK OF PROJECTION FOR 


In Fig. 13, A is a D. P. S. T. and B a T. P. S. T. knife 
switch, without fuse contacts; C is a D. P. S. T. knife switch 
with knife blade cartridge fuses, and D a D. P. S. T. knife 
switch with ferrule contact cartridge fuses. For explanation 
of the different kinds of fuse contacts see “Fuses,” page 107. 

In Fig. 13,.E and F are types of porcelain base D. P. S. T. 
switches, with receptacles for plug fuses. This type of switch 
is called a “panel cutout.” It is often used in building up 
panel boards, but may only be used to control individual cir¬ 
cuits of low amperage. 

ENCLOSED SWITCHES. —An enclosed switch is one 
having an individual protecting cover, usually of sheet metal 
which entirely encloses and protects all “live” parts of the 
switch. All projector switches are and must be enclosed 
switches, no other kind being permitted for this purpose. 
The enclosure of the switch by a metal covering is to protect 
the projectionist from possible shock by accidental contact 
with its live parts, as well as to prevent possible short cir¬ 
cuits or injury to the switch by contact with various objects. 
It is important that the covering of enclosed switches be so 
made that it cannot come into contact with the live parts, of 
the switch. 

In connecting enclosed switches it is better that the blade 
end of the switch be dead when the switch is open. In fact 
that rule applies to all switches, though sometimes circum¬ 
stances prevent its being adhered to. 

LOCATION OF SWITCHES.— In the location of switches 
local conditions must, of course, largely govern, particularly 
in the smaller theatres, but the house switchboard should be 
so located that the man in charge of it will have an unob¬ 
structed view of the screen when at the switchboard. Unless 
this be done there is apt to be an imperfect handling of the 
house lighting at the beginning and the end of the show, or at 
other points where change in the auditorium lighting may be 
necessary, no matter what care may be taken to co-ordinate 
the work of the projectionist and the work of the switchboard 
man. 

Switches governing emergency lights, which include all 
lights kept burning during the performance, should under no 
circumstances be placed on the main switchboard. You can 
never tell what an excited man will do, and in case of fire 
people inside the auditorium, including the employees, are apt 
to become excited. Some one might pull the emergency light 


MANAGERS AND PROJECTIONISTS 


95 


switches on the main switchboard, and thus set up a tre¬ 
mendously dangerous condition. Place the emergency light 
switches in the box office, where nobody can get at them but 
the ticket seller, and make him or her directly responsible for 
their handling. 

In the projection room, local conditions will govern the 
placing of switches, but it should be remembered that nothing 
can possibly be gained by making things inconvenient for the 
projectionist. Wrongly located switches often cause much 
entirely unnecessary labor and annoyance; also inconveniently 
located switches cause delay, and make the proper handling 
of the program impossible. 

The projection room incandescent lights should, as a whole, 
be governed by one switch, located within convenient reaching 
distance from working position at either projector. This will 
enable the projectionist instantly and fully to illuminate the 
room, or to cut off all lights instantly and conveniently, which 
latter-'is the best condition for projection. Each lamp socket 
should, however, have an individual snap switch. 

This is of paramount importance, because it is impractical, 
not to say impossible, under conditions usually found in pro¬ 
jection rooms, to produce the best possible screen results 
with incandescent lights burning, and the projectionist is more 
apt to extinguish his lights if there is a switch handily located 
with which he can put them all out or on with one operation 
than if he has to turn them off by using two, three or more 
switches. This is one of the seemingly unimportant points 
which is of great importance to results on the screen. See 
page 345 for modification. 

USE OF TYPES OF SWITCHES.— Except for very limited 
purposes the use of the single pole knife switch is prohibited 
by underwriters’ rules. So far as we are aware, none of the 
purposes for which a single pole switch may be used exists in 
a theatre, except in making certain rheostat connections, as 
will be explained under the heading “Rheostats.” 

The D. P. S. T. switch is the type ordinarily used to control 
all incandescent and projection circuits, except those con¬ 
trolled by triple pole or D. P. D. T. switches. The T. P. S. T. 
is used to control three-wire circuits where they enter a 
theatre, and wherever else the three-wire circuit may extend. 
D. P. D. T. switches are used in certain fuse connections, as 
will be explained under “Fuses.” These switches are also used 
for connecting two separate two-wire supply systems, and for 


96 


HANDBOOK OF PROJECTION FOR 


projection circuit connections under certain conditions. Also 
for polarity changing. 

SWITCH MARKINGS— It is required by underwriters’ 
rules that switches have certain dimensions, according to the 
voltage they are to be used on, and the number of amperes 
they must carry. 

Both the voltage and amperage capacity must be stamped 
on some part of a knife switch. Reject any switches not so 
stamped. 

A switch may be used for a less amperage and less voltage 
than it is rated to carry, but never for a higher voltage or a 
higher amperage, thus: you might use a 500 volt 50 ampere 
switch on a 110 volt circuit and to carry any number of 
amperes up to 50. But you would not be permitted to use a 
switch of less than 50 amperes capacity for 50 amperes, or a 
250 volt switch on a 500 volt circuit. The higher the voltage 
the further apart the blades of the switch must be placed, and 
the longer the switch blades must be. 

Two hundred and fifty volt switches are the type almost 
universally used in theatres. There is no such thing as a 110 
volt switch, the requirements for 110 and 250 fyeing the same. 

RECAPITULATION. —Be certain your switches have suffi¬ 
cient capacity to carry the amperage. 

Be certain your switches are of proper voltage capacity. 

Be certain your switches are so installed that the handle 
will not move downward in closing the switch. 

Be certain the hinges and contacts of your switches are 
tight and in good condition. If contacts become roughened 
they may be smoothed with 00 sand paper which should be 
wrapped around a thin strip of metal for smoothing the inside 
of contacts C, Fig. 12. 

Be sure the cross bar to which the switch handle is fastened 
is kept firmly attached to the blades. A loose, wobbly switch 
is an abomination; also it is an evidence of a careless, in¬ 
efficient workman. 

METAL CABINET. —Unless switch cabinets are built into 
the walls, all projection room switches and all other switches 
except those on the stage switchboard should be enclosed in 
a metal cabinet, such as is illustrated on page 104, the same 
to be equipped with a door which automatically closes, either 
by gravity or by a spring. 

MAIN HOUSE SWITCHBOARDS.— Main house switch¬ 
boards, particularly in medium sized theatres, are frequently 


MANAGERS AND PROJECTIONISTS 


97 


placed in the projection room, in which case the entire audi¬ 
torium lighting is under the direct care and supervision of 
the projectionist. He not only handles the switchboard itself, 
but the “dimmers,” the latter being what amounts to a series 
of adjustable rheostats by means of which various incan¬ 
descent circuits in the auditorium may be gradually dimmed 
down and finally extinguished. 

In the “National Electric Code,” copy of which may be 
secured by sending five cents in stamps to the National Board 
of Underwriters, Electric Department, 123 William Street, 
New York City, appear the following rules which must be 
strictly observed in the installation of switchboards: 

a. Must be so placed as to reduce to a minimum the danger 
of communicating fire to adjacent combustible material. 

Switchboards must not be built up to the ceiling, a space of 
three feet being left, if possible, between the ceiling and the 
board. The space back of the board must be kept clear of 
rubbish and not used for storage purposes. 

b. Must be made of non-combustible material. 

c. Must be accessible from all sides when the connections 
are on the back, but may be placed against a brick or stone 
wall when the wiring is entirely on the face. 

If the wiring is on the back, there must be a clear space of 
at least eighteen inches between the wall and the apparatus 
on the board, and even if the wiring is entirely on the face; it 
is much better to have the board set out from the wall. 

d. Must be kept free from moisture. 

e. Insulated conductors when closely grouped, as in rear of 
switchboards, must have a substantial flameproof outer 
covering. 

Flame proofing must be stripped back on all conductors a 
sufficient distance from the terminals to give the necessary 
insulation distances for the voltage of the circuit on which 
the conductor is used. 

As has been already said under “Location of Switches,” 
page 94, the location of the main house switchboard will 
depend largely upon local conditions, and may only be properly 
determined by considering the peculiarities of each individual 
case. The best location in one theatre might be the worst 
in another. 

In fixing the location, whether the switchboard be in the 
projection room or elsewhere, the architect or designer should 
be guided largely by the items accessibility and convenience, 
remembering always that if the switchboard be located out- 


98 


HANDBOOK OF PROJECTION FOR 


side the projection room it is essential it be in such position 
that the man handling it will have a good view of the screen or 
of the stage when at his post of duty. This latter is essential 
to the best manipulation of the lights, particularly if there is 
vaudeville, unless the lights be handled from the stage, as will 
most likely be the case in theatres where there is a stage. 

MATTER OF SAFETY.—If the main house switchboard 
controlling the auditorium lights be located in the projection 
room there should always be an arrangement by means of 
which the auditorium can be lighted from a suitable location 
in the auditorium itself. Also if the main house switchboard 
be located in the auditorium there should be an arrangement 
by means of which the auditorium may be lighted from the 
projection room. 

An emergency may at any time arise in which it is im¬ 
perative that the auditorium be lighted instantly. This 
emergency may arise in the projection room, as in the case of 
a film fire, and unless the projectionist himself be able to 
switch on the lights, a space of time sufficient to set up a 
dangerous condition might very likely elapse before it could 
be done from the auditorium. It is also possible that an 
emergency would arise in the auditorium itself where safety 
would demand the instant lighting of the auditorium by the 
attendants. 

It is quite possible for the projectionist to signal or tele¬ 
phone to the main switchboard attendant to switch on the 
lights, or vice versa, but in case of serious emergency the 
delay involved might be sufficient to cause a dangerous con¬ 
dition; also the signal apparatus or telephone might not be 
in good working order just at the crucial moment. 

Personally we do not favor the placing of the main switch¬ 
board in the projection room except under conditions where 
there are always two men present in the room. We have 
long since taken the position, and see no reason to change it, 
that when a photoplay is “on,’ J the projectionist should have 
nothing of any kind whatsoever to do except watch the screen 
and regulate those various things essential to a perfect screen 
result. 

If, however, there are two projectionists, as is the case in 
many theatres, or even if there is a projectionist and a helper 
always present in the projection room, then the ideal con¬ 
dition is to have the auditorium lighting, including the dim¬ 
mers, handled from the projection room. The projectionist 
may then work entirely from pre-arranged cues in the hand- 


MANAGERS AND PROJECTIONISTS 99 

ling of the whole show, including the auditorium lighting, 
and there will be no division of responsibility. A proper co¬ 
ordination of the picture, the music and the lighting is of 
paramount importance, particularly in houses where the 
music and staging of the picture have been carefully worked 
out. An effect which, if properly worked, would be beautiful, 
may be ruined by just a few seconds delay in the manipula¬ 
tion of the auditorium lighting. 

We cannot emphasize the importance of this latter too 
strongly. It was Samuel L. Rothapfel who first pointed the 
way to a truly artistic presentation of the photoplay upon the 
screen, and in the scheme of affairs as outlined by him, which 
is now followed, in greater or less degree, in all high class 
photoplay theatres, much depends upon close co-ordination 
of the auditorium lighting with the other various features of 
the program. It is therefore evident that the location of the 
main house switchboard is a matter for careful consideration 
by the management and the architect at the time the theatre 
is built. 

THE “BOARD.” —It is essential that both the projectionist 
and the man in direct charge of the theatre auditorium have a 
good understanding of the main house switchboard and its 
electrical connections. These switchboards are often imposing 
affairs, but once their connections are traced, they are simple 
indeed. 

The main house switchboard will, or should, carry every- 
circuit in the theatre, including the projection arc circuits and 
stage feeders, excepting the emergency light circuits, which 
latter must be attached to the theatre feed wires ahead of 
everything, including the main house fuses and switch, see 
page 103. 

The main house switchboard will carry the (a) main fuses, 
placed ahead (on the street side) of everything except the 
exit and emergency circuits. These fuses will carry the 
entire house load, except the circuits just named, and except 
the stage, if the stage has a separate set of service wires, 
(b) the main switch, which kills everything but the exit and 
emergency lights, (c) fuses for every individual circuit in the 
house, including the projection room and stage feeders, if the 
latter are attached to the main board, (d) service switches for 
every individual circuit, including projection room feeders 
and stage feeders. 

Of course what the main house switchboard will carry may 
be subject to modification by the peculiarities of the individual 


100 


HANDBOOK OF PROJECTION FOR 


installation. In small, strictly moving picture houses, in which 
light effects are not attempted, it is much better to have 
auditorium lights that are not used during the show ex¬ 
tinguished all at one time, rather than by pulling several small 
switches. In large houses, however, where there are many 
incandescent lights and circuits, this is neither a practical nor 
a desirable thing to do. In such houses dimers should always 
be used. 

In figure 14 we have both a digrammatic and photographic 



Figure 14. 


representation of a small 3-wire switchboard, ' commonly 
known as a “panel board.” In the diagram, A is the fuse con¬ 
tacts, B the main switch, C the house circuit fuse contacts 
and D the service switches governing individual circuits. All 
of this is seen photographically represented at the right, 
except that in the photographic representation the main 
switch and fuses are omitted, and there are five circuits on 
each “side,” instead of three. Both in the photograph and 
the diagram the screw heads connecting the individual cir¬ 
cuit feeder bars to the main circuit feeder bars form the key 
to the connection. 

Taking the diagram for example, it will be observed that 
the center or neutral bar has a screw head over the second 
and third individual circuit bars, which means that the 
neutral bar is electrically connected to these two bars, or 
in other words, to the upper bar of the lower circuit and the 
lower bar of the upper circuit. The right hand short bar is 
connected to the lower bar of the lower circuit and the left 
hand feeder bar is connected to the upper bar of the upper 
circuit. It will thus be seen that the lower circuit is con- 




















MANAGERS AND PROJECTIONISTS 



Figure 15. 



























































102 


HANDBOOK OF PROJECTION FOR 


nected to the neutral and the right hand feeder bar, so that 
it is on the right hand “side” of the three wire cuicuit. The 
neutral and the left hand bar is connected to the upper cir¬ 
cuit, so that circuit is on the left hand “side.” We thus have 
one circuit connected to each “side,” and if both circuits use 
the same number of amperes the load will be “balanced.” , 

This forms the keynote to the connections of your big 
house switchboard. It is a bit puzzling for the novice to 
trace these connections, but look at it for a while and you 
will find that in all individual circuits one side is connected 
to the neutral and the other to one or the other of the main 
switchboard feeder bars, except in the possible case of the 
use of a 220 volt motor circuit, which would connect to the 
two outside bars or wires. It will be understood that where 
there is no screw head there is no connection between the 
feeder bars and circuit bars. Thus: The left hand feeder 
bar, Fig. 14, crosses the lower second and third bars without 
electrical connection and makes electrical connection to the 
top bar at the screw head. Where copper bars of this kind 
are used instead of wires they are commonly called “bus 
bars,” though the term correctly applies to the copper bars 
which connect the power house generators to their circuits. 

Fig. 15 is a photograph of a moderately large and some¬ 
what complicated switchboard. On the right side the in¬ 
dividual circuits are indicated by X. Study the contacts 
and you will be able to trace out the connections. Taking 
the next-to-the-top right hand circuit for example, we find 
it leaves the main bus bars in the form of a three-wire cir¬ 
cuit, and that there are three plug fuses which protect the 
three-wire circuit as a whole. Just beyond the fuses is the 
handle of the T. P. S. T. switch, beyond which the upper bar 
connects to the upper wire of the upper two-wire circuit, 
the neutral connects to both the lower wire of the upper 
circuit and the upper wire of the lower circuit, and the lower 
bar connects to the lower wire of the lower circuit. 

We thus have the three-wire circuit split up into two two- 
wire circuits, at the beginning of which are the individual 
circuit fuses which must be present on all individual circuits. 
To the left this circuit starts off and ends as a plain three- 
wire circuit. Above this circuit, at the very top of the bars, 
are two two-wire circuits, the neutral bar (see Screw Head) 
connecting to the lower circuit bar, the left hand bus bar 
to the upper left hand circuit bar and the right hand bus bar 
to the upper right hand circuit bar, and thus by a little 
care in observing the screw heads, which mean electrical 


MANAGERS AND PROJECTIONISTS 


103 


contacts, we may readily trace out the connections of any 
house switchboard in which the bus bars show on the front 
of the board. If they are at the back of the board it com¬ 
plicates things a little for the beginner, but the action is 
traced out in the same manner. In Fig. 15 the main fuses and 
the 3-pole switch controlling the whole board are not shown. 

PORCELAIN BASE CUTOUT SWITCHBOARDS.— In the 

smaller theatres it is an occasional practice to build up a 
switchboard of porcelain base panel cutouts, such as are 
illustrated in Fig. 16, and at E F, Fig. 13. Any number of 
these blocks may be used, and they may be had for either 
two or three-wire circuits, but may only be used for indi¬ 
vidual incandescent light or motor circuits of low amperage. 

These cutouts 
must always be 
mounted on an 
insulating base, 
and must be pro¬ 
tected by a sub¬ 
stantial metal 
cabinet similar to 
that shown in 
Fig. 17. It is per¬ 
missible to form 
an insulating base 
for these blocks 
by placing either 
sheet asbestos or 
asbestos mill 
board not less 
than inch 

thick at their 
back. At the head of a board of this kind there should be 
a suitable knife switch having capacity equal to that of all 
the circuits of the board. This switch should carry the main 
switchboard fuses. 

If properly put together such a board is just as efficient, 
although it does not look so well as the regular slate base 
board. 

EXIT AND EMERGENCY CIRCUITS.— The feeders for 

exit and emergency circuits must, as has already been set 
forth, be tapped to the main house service wires on the 
street side of the main house switch and fuses. 

These circuits should be controlled by switches located 



Two-Wire Double Brahch, 



Three to Two-Wire Double Brahch. 


Figure 16. 






104 


HANDBOOK OF PROJECTION FOR 


either in the box office or in the manager’s office, and by no 
other switches. 

Exit and emergency lights comprise the light and exit 
signs and all lamps in entrance foyer, stairway and other 
parts of the theatre used by the audience either regularly 
or in case of emergency, and are ordinarily left burning 
during the performance. 

For the fusing of these circuits see page 120. 

STAGE SWITCHBOARD. —It is not within the province of 
this work to deal with the stage switchboard, except to point 
out a few important elements which are demanded by the 
National Board of Fire Underwriters, and which make for 
safety. 



Figure 17. 

The stage switchboard is ordinarily located on the 
proscenium wall. The common practice is to place it to the 
right of the proscenium as one looks towards the audience. 

Stage switchboards should never be installed in any theatre, 
no matter how small, without first ascertaining the Board 
of Fire Underwriters’ requirements for such installations. 

It is required that the board be protected by a sub¬ 
stantially constructed iron railing of certain height, located 
a certain distance from the board, and securely fastened to 
the floor. This guard is to protect the switchboard from 





MANAGERS AND PROJECTIONISTS 


105 



Figure 18. 


















































































106 


HANDBOOK OF PROJECTION FOR 


accidental injury by being struck with moving objects, or 
from persons falling against it, as well as to prevent such 
accidental contact causing fire. 

All fuses on a stage switchboard must be of an approved 
cartridge or plug type. It is absolutely forbidden, under 
any circumstances, to use a link or open fuse on any stage 
circuit. 

The stage switchboard should carry main fuses and main 
switch controlling all current in the board. It will, of course, 
carry the various service fuses and switches for each indi¬ 
vidual circuit. All switches should be plainly marked with 
the name of the circuit they control, thus “white foots,” 
“red foots,” “blue foots,” “first borders white,” first borders 
green,” etc. 

The utmost care must be exercised that all switch con¬ 
tacts, etc., be kept in perfect electrical and mechanical con¬ 
dition, to prevent any possibility of heating which might, 
under some conditions, be extremely dangerous, and the 
whole installation should be carefully examined at regular 
intervals to see that it is in perfect condition. 

Absolutely no one except the man in charge of the stage 
switchboard should under any circumstances be allowed to 
touch it while the performance is going on. The fewer 
people handling it at other times the better. Stage switch¬ 
boards should always be wired from the back. While this 
is not absolutely demanded, it is safer and in every way 
very much better. 

We do not care to deal further with the stage switch¬ 
board, since those contemplating the installation of one 
should accept the dictates of no authority except the city 
or state officials and the National Board of Fire Under¬ 
writers, with whom contact may be always had by ad¬ 
dressing the National Board of Fire Underwriters, Elec¬ 
trical Department, 123 William Street, New York City. 

BUILT-UP BOARD.—For those who prefer to build up a 
switchboard by using porcelain base switches, Fig. 18 will 
serve as a guide. For a small board 24 inch asbestos mill 
board makes an acceptable insulating support. Such a board 
may be built up quite inexpensively, and being installed in 
a metal cabinet such as that shown in Fig. 19, which may be 
had of any dealer in electrical supplies, will give very good 
service. The circuits marked X are incandescent circuits 
for the auditorium. 


MANAGERS AND PROJECTIONISTS 


107 


Fuses 

A N electric conductor of given size will,, as has already 
been set forth, carry only a certain given number of 
amperes of current without developing heat above 
normal temperature. See page 66 and Table No. 1 on page 70. 

Ordinarily only the number of amperes consumed by the 
various motors and lamps attached to a circuit will flow over 
the wires of the circuit, and the combined capacity of lamps 
and motors attached to any circuit is never presumed to 
exceed the rated capacity of the wires. Many things, how¬ 
ever, such as grounds, short circuits or a rise in the voltage 
may occur to cause an abnormal flow of current sufficient 
to overload wires, or if it be a rise in voltage then to over¬ 
load the apparatus attached to the wires as well. 

The fuse is a sort of electrical safety valve designed to 
act automatically and prevent overload of this kind. 



Figure 19. 

In Fig. 19, we see an elementary set of fuses diagram- 
matically illustrated. The wires of a circuit are cut and 
their ends attached to terminals A-A-A-A, these termi¬ 
nals being mounted on insulating base B. Between these 
terminals, taking the place of the copper circuit wires, are 
two lengths of “fuse wire,” which is wire composed of an 
alloy of metals, usually lead and tin, having a very low 
melting temperature and a high temperature co-efficient, 
which means that the resistance of fuse wires rises rapidly 
with overload. 


















108 


HANDBOOK OF PROJECTION FOR 


The practical operation is as follows: The current 
capacity of the fuse wire is in no case presumed to exceed 
the rated capacity of the wires of the circuit they protect, 
and only to exceed the combined current consuming 
capacity of the lamps, if it be an incandescent light circuit, 
by a small margin, and only to exceed the combined current 
consuming capacity of the motors, if it be a motor feeder 
circuit, by 25 per cent. 

Should the current flow increase, by reason of short cir¬ 
cuit, grounds or rise in voltage, by an amount sufficient to 
cause overload, the fuse wire would become hot quickly, 
and, its melting temperature being far below that which 
would injure a copper wire, the fuse will melt and stop all 
current flow before the wires of the circuit, or even the 
apparatus attached thereto could be injured. 

Assume, for example, a circuit of R—C wire rated at six 
amperes, with a sufficient number of incandescent lamps 
attached thereto to consume a total of five amperes. We 
would insert between the terminals in Fig. 19 fuses having 
a capacity of 5 amperes. As a matter of fact our 5-ampere 
fuses would actually carry more than that, because fuses 
are designed and intended to carry 10 per cent, more than 
their rated capacity, in order to allow for ordinary fluctu¬ 
ations in voltage. 

Fuses protect a circuit because they melt at a temperature 
far below that necessary to injure copper wires. 

Fuses protect the apparatus because they heat very 
quickly under overload, melt and stop all current flow before 
sufficient time has elapsed to injure lamps or motors. 

Not only is the fuse a safeguard in the way we have de¬ 
scribed, but it is also an insurance against the operation of 
a faulty circuit. Because if the attempt is made to install a 
new fuse before the trouble which caused the blowing of 
the old one has been remedied, the trouble which blew 
(melted) the old fuse will also blow the new one. 

The foregoing is the theory of the fuse and an explana¬ 
tion of its practical operation. In practice, however, raw 
fuse wire is now seldom employed, and never in a theatre, 
except in the form of “link” fuses, which are permitted, and 
even required by some cities for the fusing of projection 
circuits, but they are located in a fireproof proiection room 
and must be placed inside an iron cabinet as well. 

The types of fuses with which the motion picture pro¬ 
jectionist is likely to come into contact, are the “plug” and 


MANAGERS AND PROJECTIONISTS 


109 


the “cartridge,” both of which forms are in general use in 
theatres. In fact, they are the only fuses used in theatres, 
except as before noted with relation to the link fuse. 

In Fig. 20, A is a cartridge fuse having “ferrule” (see 
XX in figure) contacts, and B is a cartridge fuse having 
knife blade contact, the first named being permitted only 
on circuits carrying 60 amperes or less. C and D are re¬ 
spectively the receptacles for fuses A and B. 

CARTRIDGE FUSES. —A cartridge fuse consists of two 
terminals joined by a barrel constructed of insulating 



material. Inside this barrel is a conductor made of fuse 
metal, which connects the two terminals, and a small wire 
known as the “pilot” wire also connecting the terminals and 
passing under a round spot on the paper label attached to 
the fuse, as per illustration in Fig. 21. An air chamber is 
used in some fuses, the idea being that the heat conduction 
through the confined area being slow, the temperature of 
that part of the fuse will rise rapidly, and always in the 
same ratio, which is persumed to establish a practically 
constant point of blowing. Except in the air chamber the 
fuse wire is surrounded by a powdered, non-conducting sub¬ 
stance, designed to instantly break the arc when the fuse 
blows. On a paper label pasted on the outside of the 
barrel of the fuse is a small round spot under which the 
pilot wire passes. When the fuse blows the arc formed 
when the pilot-wire melts is presumed to char the paper, 
and thus turn the spot brown or black, although it does not 
always perform its duty in this respect. Table No. 4, which 






110 


HANDBOOK OF PROJECTION FOR 


is taken verbatim from the National Electric Code of Fire 
Underwriters, gives the essential underwriters’ require¬ 
ments in the matter of dimensions for cartridge fuses. The 
underwriters require that the contacts have a certain 



0/9/?/ /v ero /=*<>»*or/rro, /A'-st/t. *rr/A/<£ 


Figure 21. 


minimum area, that the paper barrels have a certain mini¬ 
mum length and diameter, and that the fuses have a certain 
definite length over all for a given voltage and amperage. 

PLUG FUSES. —Plug fuses are freqently used to protect 
theatre incandescent circuits. A plug fuse consists of a 
receptacle similar to that illustrated at B, Fig. 22, and a 
porcelain “plug,” with a cap, usually of brass, as per A, 
Fig. 22, the brass cap which may or may not have a mica 
window through which one is presumed to view the fuse 
and ascertain its condition. Usually, however, this is not a 
practical thing to do, and the condition of the fuse may only 



Figure 22. 


































MANAGERS AND PROJECTIONISTS 111 

be definitely ascertained by testing as hereinafter directed. 
C, Fig. 22, shows the porcelain base of the fuse plug with 
the cap off and the fuse in place. D, Fig. 22, is a special 
form of plug fuse to be used on amperage between 35 and 60, 
plug fuses in their regular form not being made in excess of 
35 amperes capacity. They are not made in any form for 
capacity in excess of 60 amperes. Plug fuses may be used 
for any kind of work desired, up to the limit of their 
capacity. They are just as safe, and somewhat cheaper than 
cartridge fuses. 

LINK FUSES.— The link fuse, illustrated in Fig. 23, is 
specified for use on projection circuits by the authorities of 



New York City and by some other municipalities. This is 
by reason of the fact that it is difficult to “boost” a link fuse 
without the inspector being able to instantly detect the 
fraud. 

Where link fuses are used for projection circuit pro¬ 
tection they must be located in a metal cabinet having a 
self-closing door, and this cabinet must itself be located 
inside the projection room. 

The link fuse consists of copper terminals A A, Fig, 23, 
and fuse wire B, terminals A A being clamped under the 
terminal screws of a link fuse block. 

BOOSTING FUSES. —Boosting a fuse consists in in¬ 
creasing its capacity by means of a small copper wire, or in 
case of a plug fuse a copper coin or something similar. 
Such practice is reprehensible in the extreme. It is, in fact, 
next door to criminal. A fuse is for the protection of wires 
and apparatus, and a boosted fuse no longer serves its 
purpose. It leaves the circuit without any protection at all, 
under which condition there is a possibility of serious 
damage to the apparatus, and of heating the circuit wires 
to the point where they will set the building on fire, or be 
fused by the heat. 

With both cartridge and plug fuses it is possible for a 
projectionist possessed of more cunning than good sense to 



112 


HANDBOOK OF PROJECTION FOR 

TABLE OF DIMENSIONS OF THE 
STANDARD CARTRIDGE 



6TYUC or 

terminal row osrvriMOCiE ry^C5 
O- fcO AMPCRCft 

j 


Ponu 1. 

CARTRIDGE 

FUSE—Ferrule 

Contact. 

Voltage 

Rated 

Capacity. 

Amperes 

A 

B 

C 

Length 

Over 

Terminals. 

Inches. 

Distance 

between 

Contact 

Clips. 

Inches. 

Width 

of 

Contact 

Clips. 

Inches. 

Not over 


H 





250 

0-30 

a 

2 

1 


V 2 


31-60 

u 

£ 

3 

m 

% 


61-100 

M 

5% 

4 


% 


101-200 

g 

7% 

4Ya 

1*4 


201-400 

8 

8% 

5 


1% 


401-600 

£ 

10% 

6 


m 

Not over 


H 





600 

0-80 

a 

5 

4 


% 


31-60 

i* 

0 

5% 

4*4 

% 



U. 






61-100 

N 

7% 

6 


9J/ 


101-200 

a 

9% 

7 




201-400 

tu 

11% 

8 


1% 


Table 














































MANAGERS AND PROJECTIONISTS 113 

NATIONAL ELECTRICAL CODE 
ENCLOSED FUSE 


— 


__! 

r~ 


~v~ 

G 

— 


f 

. i . 

— 

JiZ 



Porm 2. CARTRIDGE PUSE— Knife Blade Con¬ 
tact. 


D 

E 

F 

G 


Diameter of 
Ferrules or 
Thickness 
of Terminal 
Blades. 
Inches. 

Min Length 
of Ferrules 
or of Termi¬ 
nal Blades 
outside of 
Tube. 

Inches. 

Dia 

of 

Tube. 

Inches 

Width 

of 

Terminal 

Blades. 

Inches. 

Bated 

Capacity. 

Amperes. 


% 

Vs 

rH 

g 

0-30 

u 

% 

% 

B 

£ 

31-00 

Vs 

1 

1 

% N 

61-100 

•fis 

1% 

1% 

g 

101-200 

*4 

1% 

2 


201.400 

Vl 

2^4 

zv 2 

2 £ 

401-600 

a 

% 

% 

rH 

0-30 

1* 

% 

i 

u 

Si-60 

% 

A 

1 


% N 

61.100 

1% 

i4 

8 

101.200 

2 

1% 

% 

1% Uh 

201400 


Number Four. 
























































114 


HANDBOOK OF PROJECTION FOR 


increase the capacity of his fuses almost indefinitely by 
'“boosting,” and such a trick could only be detected by a 
very close inspection. With the link fuse, however, this 
cannot be done so readily. Hence link fuses are recom¬ 
mended, under the conditions of installation named, for pro¬ 
jection circuits. 

Any projectionist or other person caught boosting fuses 
should be instantly discharged, and if he holds a license it 
should be suspended for a first offense and revoked for a 
second. 

Never fuse above the rated capacity of the wires of the 
circuit. 

Never fuse an incandescent lamp circuit above the com¬ 
bined amperage capacity of its lamps. 

Never fuse a motor circuit above the rated capacity of the 
wires, or more than 25 per cent, in excess of the rated 
capacity of the motor or motors. 

Underwriters’ rules allow the fusing of a motor circuit to 
25 per cent, above the capacity of the motor or motors 
attached thereto, provided, of course, the wires be large 
enough to accommodate the capacity of the motors plus the 
25 per cent, overload. 

It is physically possible to refill both cartridge and plug 
fuses, but it does not pay to do so, except in the case of 
special fuses made to be refilled. 

THROW OLD FUSES AWAY unless they be of the “re¬ 
filling” sort. Fuses which have blown have absolutely no 
commercial value. They should be thrown away imme¬ 
diately, else they may get mixed with the good fuses, with 
consequent possibility of vexatious delay—and such delays 
usually occur just at the worst possible time. If you keep 
your old fuses, and get them mixed with the good ones, for 
such delays you have no one but yourself to blame. 

FUSING THE PROJECTION CIRCUIT.— The projection 
circuit wires are usually of size amply capable of carrying 
considerably more current than will ordinarily be used. 
Both the lamp and the wires of the circuit offer no chance 
of damage through a considerable temporary overload. It 
not only is a nuisance, but also impractical to have pro¬ 
jection room luses constantly blowing, and since the re¬ 
sistance oi a projection arc lamp, especially if it be hand 
fed, is a highly variable quantity, the current flow will 
under any conditions vary considerably. We would there¬ 
fore recommend for projection circuits the following, with 


MANAGERS AND PROJECTIONISTS 


115 


the understanding that the ordinary current flow at the 
arc is what is referred to under the heading “normal 
amperage.” Of course if the fusing is only done on the 
primary of a transformer (Compensarc Inductor Econo¬ 
mizer, etc.) then due allowance must be made, as is set 
forth, see bottom of this page and next page. 

Note—Fuses cannot be had in all the sizes named. This 
acts to limit the application of table No. 5. 


Normal Arc 
Amperage 

Fuse to 

Necessary 
size R. C. 
portion of 
circuit wires 

Necessary 
size asbestos 
covered portion of 
circuit wires 

20 

25 

6 

6 

25 

30 

6 

6 

30 

35 

6 

6 

35 

45 

6 

6 

40 

55 

5 

6 

45 

60 

4 

6 

50 

75 

3 

5 

55 

80 

3 

5 

60 

85 

2 

5 

70 

95 

1 

4 

80 

100 

1 

8+8 

00 

110 

0 

6+8 

100 

125 

0 

6+8 

110 

135 

00 

6+6 

120 

150 

00 

6+6 


Table No. 5. 


Projection circuit fusing table where rheostats are used 
for resistance. 

Note—Asbestos covered stranded wires are not available 
in a size larger than No. 4. We have, therefore, given the 
necessary sizes for doubling. “8 + 8” means two No. 8 wires 
instead of the necessary No. 3 for 100 amperes, and a 6 and 
an 8 for 110 amperes. 

Explanation—Wires must be large enough to accommo¬ 
date the amperage capacity of the fuses without overload¬ 
ing. That portion of the circuit which is asbestos covered 
wire may be treated as weatherproof in this respect. See 
wire capacity table, page 70. 

FUSING PROJECTION CIRCUIT FOR MOTOR GENER¬ 
ATOR. —Fusing the projection circuit where a motor gener¬ 
ator rotary converter or mercury arc rectifiers is used is a 
simple matter. Ordinarily there should be fuses on both the 
motor and the generator side—on the intake and the output. 
Ascertain the amperage at the arc under normal conditions, 
and add about 20 per cent, to that amount, which will give 
the c.orrect size for your fuses on the generator, or output 


116 


HANDBOOK OF PROJECTION FOR 


side. The arc will, of course, be D. C., and for the purpose 
of figuring, the table on page 400 should be used. If, for in¬ 
stance, we have a 60-volt arc, the result of the arc amperage 
multiplied by 60 will give the arc wattage, which, divided by 
the voltage of the supply lines will give the intake amperage, 
or would give it if the machine had 100 per cent, efficiency. 
Few such machines, however, have more than a 65 per cent, 
efficiency; therefore, to the result so obtained, about 35 per 
cent, must be added in order to get the actual intake amper¬ 
age thus: Assuming a line voltage of 110 and an arc wattage 
of 4200 (70 amperes with a 60 volt arc), then 4200 watts 
110 volts = 38+ amperes, which, with the addition of 35 per 
cent, for losses in the machine itself, would be the amperage 
taken from the line. 35 per cent, of 38 amperes is 13 3/10th 
amperes, and, disregarding fractions, 13 + 38 = 51, which 
would be the total amperage taken from the line. 

Of course, in the foregoing we are merely showing you how 
the thing is done. In order to get anything like an accurate 
result it would be necessary to measure your arc voltage with 
a voltmeter, and to measure the efficiency of your motor 
generator and the latter is not a thing the ordinary projection¬ 
ist is equipped to do with any large degree of accuracy. 

Assuming, however, that we find the intake amperage to 
be 51, we would install 55 ampere fuses on the intake line, to 
protect the motor, and since the generator output is 70 
amperes it would only be necessary that we install seventy 
ampere fuses on the generator side, unless it were necessary 
to overload the machine at change-over, under which condi¬ 
tion we would necessarily fuse for the overload, whatever it 
might be. 

The foregoing is, however, qualified by the fact that if the 
generator is of higher voltage than the arc, then the arc 
amperage must be multiplied by the voltage of the generator 
instead of the voltage of the arc, since resistance will have 
to be used to cut down the voltage of the generator to the 
arc voltage, and voltage consumed in resistance counts just 
the same as that used in operating the arc. 

SUPPLY OF FUSES.—The careful man will always keep 
plenty of fuses on hand. One never can tell when a fuse will 
blow. Sometimes an epidemic of fuse blowing occurs. It is 
bad to be caught without fuses, and the only insurance 
against it is an ample stock of surplus fuses. 

In case you do get caught without fuses it is possible to 
protect the circuit reasonably well for a temporary period 


MANAGERS AND PROJECTIONISTS 


117 


with one fuse, bridging the other fuse terminals with a 
copper wire. This, however, may only be tolerated as a 
strictly temporary expedient in case of emergency, until 
proper fuses can be procured. Emergencies of this kind 
should never occur. 

A better ^emergency substitute is to make a fuse of copper 
wire. While such a fuse would be unreliable to a consider¬ 
able extent, and from every viewpoint objectionable, still it 
may be used temporarily in an emergency to bridge one fuse 
contact, provided the other fuse be in good condition. W"e 
therefore give the fusing point of small copper wires. 


TABLE NO. 6 


Fusing Point of Copper Wires. 

American (B. & S.) Wire Gauge Fusing Current in Amperes 

30 10 

28 15 


26 

25 

24 

22 

21 

20 

19 

18 

17 

16 

15 

14 

13 


20 

25 

30 

40 

50 

60 

70 

80 

100 

120 

140 

160 

200 


By combining strands of an asbestos covered wire, which 
usually are either No. 30 or 31, a fuse of almost any desired 
capacity may be had. Thus, five strands would be about 
right for 40 amperes. 

WHEN FUSES BLOW. —When a fuse blows and the new 
one you install also immediately blows, it is conclusive proof 
that there is heavy overload, most likely due to a “short” or 
“ground,” and the circuit must be left dead until the trouble 
is located. See testing for grounds, page 356. 

A rise in voltage will operate to force more current through 
the lamps and motors, thus causing an increase in amperage 
which may blow the fuses. This condition will make itself 
evident by the incandescent lamps burning above candle 
power. 

FUSE CONTACTS.— Should a fuse blow and the new one 
installed also blow, but only after a more or less extended 
time, it is likely the trouble will be found in the fuse con¬ 
tacts. 

Examine the fuse contacts carefully, since loose or dirty 


118 


HANDBOOK OF PROJECTION FOR 


contacts will generate heat, which may be sufficient to cause 
the trouble, especially if the fuses are working near their 
capacity. 

TESTING FUSES. —Often when fuses blow it is difficult 
to tell which one of the two it is. We would therefore recom¬ 
mend the installation, at some convenient point, of a fuse 
tester made as per Fig. 24, in which A and B are the wires 
of any circuit that is always “alive,” preferably the main 
feeders ahead of the switchboard fuses. If you attach at 
this point and the house is fed by a three-wire system, be 



sure to attach to one outside wire and the central or neu¬ 
tral wire, else you will have 220 volts on your tester instead 
of 110. D is an ordinary cartridge fuse receptacle, which 
must be ferrule or knife blade, according to the type of fuses 
used. E is a plug fuse receptacle. C is a receptacle and an 
incandescent lamp of the voltage of your current. When you 
put a fuse in either of the receptacles and lamp C does not 
light the fuse is worthless, and should be thrown away. 

FUSE MARKINGS. —Cartridge fuse voltage and amperage 
rating are usually found marked on the paper label of their 
barrel. Plug fuses have their ratings stamped on the brass 
cap or the center contact and link fuses have, or should’have 
their rating stamped on one of the copper contacts. 































MANAGERS AND PROJECTIONISTS 119 

WHERE FUSES ARE INSTALLED.— In general, fuses 
are installed as follows: (A) Main service fuses, located 

ahead (on the street side) of the main house switch. These 
fuses carry all the current used in the theatre except the 
exit and other lights ordinarily left burning during the per¬ 
formance. Circuits carrying these latter, called emergency 
lights, should be attached to the feed wires ahead (on the 
street side) of everything else, and have service fuses of 
their own. See “Fusing Emergency Light Circuits,’’ page 120. 

Note—In some theatres the stage is fed by a separate set 
of feeders coming from the street mains, in which case this 
circuit will, of course, have main fuses of its own. (B) Fuses, 
usually on the main house switchboard, protecting the pro¬ 
jection room service circuit. (C) Fuses on the main house 
switchboard protecting the service wires for the stage, if the 
stage takes its current through the main switchboard, as is 
usually the case. (D) Main fuses in the projection room 
which protect all projection room circuits; also individual 
service fuses on every separate projector arc circuit and 
projection room motor and incandescent circuit. (E) Fuses, 
ordinarily located on the main house switchboard, for each 
individual auditorium incandescent and motor circuit. (F) 
Fuses on the stage switchboard for each individual circuit, 
as well as main fuses carrying all stage circuits. (G) Fuses, 
usually located in the box office, carrying the entire emer¬ 
gency light system, as well as fuses for each individual 
emergency light circuit. (H) Fuses for each individual 
emergency light, particularly in the case of exit lights. (1) 
Fuses must be installed wherever a change in size (diameter) 
of wire occurs. 



Figure 25. 










































120 


HANDBOOK OF PROJECTION FOR 


FUSES FOR EMERGENCY LIGHT CIRCUITS— Main 

fuses for emergency light circuits should be located ahead 
(on the street side) of everything else, including the main 
house switch. In addition to this, every separate emergency 
circuit must have fuses of its own, and still in addition to this 
it is an excellent plan to fuse each individual emergency 
light, especially the exit sign lamps, with one-ampere fuses. 
This latter is by reason of the fact that if trouble develops 
in a lamp, it will then blow only its own fuse, without dis¬ 
turbing the other emergency lights, where otherwise it would, 
or at least might put an entire circuit, or possibly even the 
entire emergency light system, out of business. 

Every circuit, no matter how large or small it may be, must 
be protected by its own individual fuses, in addition to the 
main fuses carrying all circuits. 

DOUBLE FUSING PROJECTION CIRCUITS.— The blow¬ 
ing of projection circuit fuses is a very annoying thing, since 
it stops the show and causes delay while new fuses are being 
installed. It does not necessarily follow that there is any¬ 
thing wrong because a projection arc lamp circuit fuse blows, 
particularly if the circuit is not fused much above the amper- 
.age being used. By installing two sets of projection circuit 
fuses as per Fig. 25, delays of this kind are avoided. When 
a fuse blows the projectionist has only to throw over the 
D.P.D.T. switch to cut in a new set of fuses, and unless 
there be something wrong with the circuit itself no appre¬ 
ciable delay will occur. 


PUNCHING HOLES IN 
FILM IS NOTHING LESS 
THAN A CRIME. THE 
MAN WHO DOES IT 
SHOULD BE DISCHARGED 
IMMEDIATELY. 



MANAGERS AND PROJECTIONISTS 


121 


Wire Terminals and Wire 
Splices 

I N the course of his duty it is necessary that the projec¬ 
tionist on the road with a traveling show, or the pro¬ 
jectionist of the small-town theatre do more or less wire 
work, or at least that he have an understanding of many 
things connected with wire work. 

TERMINAL LUGS. —Every wire should have a terminal 
lug, and except in cases where lugs will be subjected to heat, 
as in the projector lamp-house or at the rheostat, they 
should be soldered to the wire. Terminal lugs come in a 
number of forms, two of which are illustrated at E F, Fig. 26. 
In soldering a lug to the wire, proceed as follows: First 
measure the depth of the socket in the lug and cut off just 
sufficient of the insulation of the wire to allow its end to 
reach the bottom of the hole in the lug. Make the cut a 
square one, but be very careful not to cut clear through 
against the wire, because if you do the edge of your knife 
will most likely cut a tiny ring in the outside of the wire, 
which will to a large extent act the same as the cut made 
on a glass by a diamond. A knife cut on the outer surface 
of a copper wire weakens it greatly, so be careful. 

Having removed the insulation, as per B, Fig. 26, scrape 
the bare wire-end perfectly clean. This latter is important, 
since otherwise the solder cannot make perfect contact be¬ 
tween the wire and the lug. Next, first having made sure 
the inside of the socket of the lug is perfectly clean, hold 
the lug in the flame of a blow torch, or some other heat 
source, and melt sufficient solder into it to fill the hole about 
half full. Don’t get the lug too hot, but just hot enough to 
make the solder thoroughly liquid. Now, first having rub¬ 
bed on the bare wire end a little paste soldering flux, shove 
it down into the solder in the lug and hold it then until the 
solder cools. 

CAUTION: Do not shove the wire into the lug with a 
quick push. If you do, the hot metal will probably squirt 


122 


HANDBOOK OF PROJECTION FOR 


out and you may get badly burned. If the weather is cold 
it will be well to warm the end of the wire a little before 
shoving it into the lug. If these directions are followed you 
should have a mechanically strong and a perfect electrical 
joint. 

In attaching terminal lugs to binding posts, be very sure 
that both lug and the binding post are perfectly clean. If 
they are not, scour them with a bit of sandpaper or emery 
cloth, or scrape them clean with a knife blade. It is par¬ 
ticularly important that a copper wire be perfectly clean 
when it is joined directly to a binding post without a lug, 
since often a thin coating of oxidization will cover the metal, 
and this coating, while it is usually thin enough to be in¬ 
visible, offers high resistance. A wire attached to a binding 
post by means of a properly soldered lug should offer no 
more resistance than the same length of the wire itself would 
offer, but if the connection be improperly made it may offer 
considerable resistance—perhaps enough to make the joint 
hot. This will itself operate to still further increase the 
trouble, since heat increases the resistance of metals. 

The resistance of one imperfect joint might or might not 
amount to much, but that of several would waste many 
.dollars worth of electrical energy in the course of a year, 
and it is well to remember that the meter registers all energy 
consumed, whether it be used in overcoming the useless re¬ 
sistance of poorly made joints, or in the production of light. 



Figure 26. 

















MANAGERS AND PROJECTIONISTS 


123 


WIRE SPLICES. —In Fig. 26 several correct methods of 
making splices are illustrated. First the insulation must be re¬ 
moved from the ends of the two wires to be joined for a dis¬ 
tance of from 2 to 3 inches, according to the size of the wire. 

The insulation should be whittled away just as you would 
whittle a lead pencil in sharpening it. Do not cut the insula¬ 
tion square off by running the knife blade around the wire. 
It makes a neat looking jub, but the knife blade is apt to cut 
a slight ring around the wire, which, as before set forth, acts 
much as does the scratching of the surface of glass with a 
diamond, causing the wire to break very easily at that point. 
The correct method of trimming off the insulation for the 
making of a splace is shown at A, Fig. 26, and the wrong way 
is illustrated at B. 

After removing the insulation, the wire ends must be thor¬ 
oughly cleaned, until they shine. This may be done with 
emery or sandpaper, or by scraping with a knife blade. Un¬ 
less the wire be made perfectly clean there will not be good 
electrical contact. After being thoroughly cleaned the wire 
ends must be twisted together tightly, as at I, Fig. 26, after 
which the joint must be soldered. 

Underwriter’s rules provide that a wire splice must be 
made both mechanically and electrically perfect before sol¬ 
dering. 

To solder, wet the metal thoroughly with a soldering fluid 
or its equivalent, which latter may be had from electrical 
dealers in stick or paste form. After thoroughly covering 
the joint with the fluid, or rubbing paste or stick flux on, 
hold both the wire and the end of a piece of wire solder in 
the flame of a blow torch until the solder melts and runs all 
through the joint. 

CAUTION. —Care must be observed not to get the wire too 
hot, especially with small wire, since too much heat causes 
injury to the copper, reducing both its tensile strength and 
carrying capacity. If too much heat is used the solder will 
run through and out of the joint. If the soldering be proper¬ 
ly done the joint will have greater mechanical strength and 
carrying capacity than the wire itself. 

After soldering, the wire must be wrapped with insulating 
tape to the depth of the original insulation, the first layer 
of which should be what is known as rubber tape, with an 
outer covering of ordinary adhesive cloth tape. 

What is perhaps the best method of making a splice ic 


124 


HANDBOOK OF PROJECTION FOR 


asbestos covered stranded wire is illustrated at C, Fig. 26, ex¬ 
cept that the strands should be divided into about six groups. 

Under some conditions a wire connector similar to D, Fig. 
26, may be used, but wire connectors such as this cannot be 
used to join the ends of stranded asbestos covered wire, or 
other stranded wire, unless the ends of the wire be first run 
full of solder, thus binding the strands together in a solid 
mass. 

SOLDER FLUX. —An excellent soldering fluid is composed 
of the following. The mixture may be compounded by any 
druggist. It works well on either copper or tin. 


Saturated solution of zinc chloride.5 parts 

Alcohol .4 parts 

Glycerine .1 part 


TERMINAL LUGS FOR HOT WIRES.— There is a num¬ 
ber of terminal lugs designed to be used without solder 
where the service is such that a soldered terminal would be 
impractical, as in the case of old style projection arc lamps, 
rheostat binding posts, etc. These lugs make contact with 
the wires by means of compression. In attaching them be 
certain the metal of both the wire and lug is perfectly clean. 
They were in common use before projector manufacturers 
began equipping their arc lamps with clamps to receive the 
wire in such form that terminals are no longer required for 
that service. They may still be had from supply dealers, and 
are suitable for connecting the wires to rheostat binding 
posts, although most modern rheostats will permit of the 
use of a soldered lug, especially if a rather hard solder be 
used. The soldered terminal is much the best. 


GO TO WORK EACH DAY AS 
THOUGH IT WERE THE FIRST 
DAY ON A NEW JOB AND YOU 
HAD TO MAKE GOOD. 






MANAGERS AND PROJECTIONISTS 


125 


Lenses 

T HERE is a law which deals with light action with rela¬ 
tion to its intensity at different distances from its 
source as follows: 

“Light intensity decreases inversely as the square of the 
distance from its source.” 

This is illustrated in Fig. 27 A, and in Fig. 36 H. It is 
mentioned here to caution you that this law applies to light 
from an open light source only, because many have com¬ 
mitted the blunder of applying it to the light beam between 
the projection lens and the screen. The law does not apply 
to light after it has been acted upon by a lens. 

In Fig. 27A, A. B and C represent screens held before an 
open light source at different distances therefrom. Remem¬ 
bering that light travels in straight lines, it is readily seen 
that screen A would receive all the rays falling within the 
two black, diverging lines, and that screens B and C could 
only receive the relative portions as indicated. See further 
explanation accompanying Fig. 36 H, page 162. 

OPTICAL TRAIN. —The optical train of the motion picture 
projector is made up of two entirely separate lens com- 










126 


HANDBOOK OF PROJECTION FOR 


binations, optically so joined that they become, in effect, a 
compound lens system. 

THE CONDENSER AND ITS FUNCTION.— The first 

element of the system is the condenser, the function of 
which is to receive the diverging rays from the light source, 
refract and converge them to what is known as the “spot” 
at the projector aperture. Put another way, the office of 
the condenser of a motion picture projector is to direct 
upon the projector aperture the greatest possible amount 
of the total available light. 

THE FUNCTION OF THE PROJECTION LENS.— The 

second element of the system is the projection lens. Its 
function is to receive the diverging light rays carrying the 
film image, and to refract and focus them at the screen in 
an enlarged, reversed image of the film picture. 

TECHNICAL TERMS. —There are many technical terms 
used in connection with lenses and optics, but we believe 
that, insofar as concerns the projectionist, only a few are of 
any considerable importance. 

PRINCIPAL AXIS. —The principal axis of a lens is an 
imaginary line which passes exactly through the center of 

its diameter, and is exact¬ 
ly perpendicular to its 
plane, remembering that 
in optics “perpendicular to” 
means at right angles to. 

In Fig. 27 point F is the 
center of curvature of the 
surface of the lens far¬ 
thest away from it. Line 
F A is the principal axis 
of the lens, because it is 
perpendicular to line B, at 
the center of the diameter 
of the lens and line B is 
the plane of the lens. It 
will thus be seen that if 
line F A were a ray of 
light it would not be re¬ 
fracted, because it would 
meet both surfaces of 
the glass exactly at 
right angles, or, in 












MANAGERS AND PROJECTIONISTS 


127 


optical terms, would be perpendicular to both surfaces of 
the lens, hence would pass straight through. 

Let us also examine line C, which, too, will meet one sur¬ 
face of the lens, the one farthest from point F, exactly at 
right angles, because any line drawn from a point of curva¬ 
ture will be exactly perpendicular to the surface at the 
point it meets it. In Fig. 27 line D is intended to represent the 
surface of the lens exactly at the point line C meets it. 

But, as a matter of fact, if line C be a ray of light it will 
not continue straight through as shown, but will be re¬ 
fracted by the first surface, because it meets the surface at 
an angle, and will follow the path indicated by the dotted 
line. Likewise line G would be perpendicular to the lens 
surface at E, if it were continued straight through. But it 
is refracted by the first surface, and refracted very much 
more than line C because it meets the glass at a much 
greater angle. 

Neither line C or line G is a principal axis, because neither 
is perpendicular to the plane of the lens as represented by 
line B. 

CONJUGATE FOCI. —Conjugate foci is a term having 
reference to two points, one being the distance of the optical 
center of the lens from a light source,* or from an object, 
and the other the distance from the optical center of the 
lens to the point at which the rays from the light source 
or object are focused into an image. The conjugate foci 
points are shown in Fig. 30, in which object X (candle) is 
one point and the image, Y, the other. Altering the dis¬ 
tance of the object from the lens automatically alters the 
distance of the image. If the candle (Fig. 30) be moved 
nearer the lens, then image Y will automatically be re¬ 
moved further away, and vice versa. In a projector optical 
train the conjugate foci points of the condenser are the 
light source and the image of it which is formed near the 
“spot,” while the conjugate foci points of the projection lens 
are the film and the screen. 

REFRACTION.— The action of lenses is based upon the 
following: 

Light rays travel in straight lines in any transparent 
medium of even density, but are bent or refracted while 
passing from a medium of one density to a medium of 
another density, provided the rays enter the second medium 
at an angle to its surface. 


128 


HANDBOOK OF PROJECTION FOR 


It therefore follows that, glass and air being of different 
density, if rays of light pass from one to the other at an 
angle to the surface of either medium, they (the rays) will 
be bent, or “refracted.” Concerning this, “Optic Projection,” 
page 576 says: 

“The amount of bending depends upon two conditions; 

(1) The greater the angle of incidence of the light, that is, 
the further from the perpendicular or normal that the light 
strikes the surface, the greater will be the bending upon 
entering the second medium. And this increase is not simply 
with the increase of the angle of incidence but propor¬ 
tionally greater, that is, in accordance with the law of sines. 

(2) The bending depends also upon the difference of den¬ 
sity of the two transparent media. If the difference is great, 
the refraction will be great, and if the difference of density 
is small, the refraction will be proportionally small.” 

It is not the purpose of this work to instruct in optics, 
except insofar as we feel is necessary to give the pro¬ 
jectionist a broad understanding of lens action. We do not 
expect to enable him to determine the refractive index of 
glass, but we do expect to give him a comprehensive under¬ 
standing of how and why a lens refracts rays of light, and 
focuses light rays to an image. 



In Fig. 28 we see three rays of light incident upon a simple 
bi-convex lens. Ray A strikes the lens surface at a com¬ 
paratively heavy angle, hence is bent (refracted) at a heavy 
angle. Ray B strikes the surface of the lens at a less angle, 
hence is refracted in less amount. Ray C strikes the glass 
perpendicular to its surface hence is not refracted at all, 
but passes straight through. 







MANAGERS AND PROJECTIONISTS 


129 


Since air and glass are always the mediums for trans¬ 
mission of light, insofar as concerns the projectionist, and 
the density of glass varies but little, we may roughly as¬ 
sume that the amount of refraction the rays will receive 
from a lens will be dependent almost entirely upon the 
angle at which it encounters the surface of the glass, either 
in entering or leaving the lens. 

Those who wish to know why the rays are bent under the 
conditions named will find the explanation in any good, 
work on physics. It seems hardly worth the space to set 
forth the matter here. 

ANGLE OF INCIDENCE. —The angle of incidence is the 
angle the entering rays makes with a line perpendicular to 
the surface of the medium. 

ANGLE OF REFRACTION. —The angle of refraction is 
the angle a ray makes with a line perpendicular to the surface 
of the medium after leaving it. 

WORKING DISTANCE.— See page 49. 

EQUIVALENT FOCUS (E. F.). —A term applicable to 
compound lenses consisting of two or more individual ele¬ 
ments, as in the case of the projection lens. It means that 
the combination will possess the same power of reduction 
or magnification possessed by a single, simple lens having 
the same focal length as the equivalent focus of the com¬ 
bination. For instance: If your projection lens is a 4.5 
inch equivalent focus (E. F.) then it will, when working 
under the same conditions, project the same size picture 
that a single lens of 4.5 inch focus would project. Equiva¬ 
lent focus is of value to the projectionist in computing the 
focal length lens required to project a given size picture at 
a given distance. See page 155. 

SPHERICAL ABERRATION.— Spherical aberration is 
that quality of a simple lens which causes it to focus rays 
which pass through it at varying distances from its prin¬ 
cipal axis at different distances from its optic center. The 
professors Gage, in their book, “Optic Projection,” define 
it as “the unequal bending of the light rays in different 
zones of a lens.” This we do not regard as correct as to 
language (although what is meant is correct enough), be¬ 
cause naturally the rays will be bent unequally in different 
zones of a lens. Were this not so there could be no reduced 
or magnified image with parallel rays incident. 


130 


HANDBOOK OF PROJECTION FOR 


Rays passing through the outer edge of a simple uncor¬ 
rected converging lens cross the principal axis of the lens 
at a point nearer its optic center than do rays passing 
through the lens nearer its principal axis. This is illustrated 
in Fig. 29. 

CHROMATIC ABERRATION.— Avoiding a technical 
definition, chromatic aberration is that quality of a lens which 



causes it to separate white light more or less into its primary 
colors. It is a quality of simple lens action which causes it 
to focus different color waves at different points or distances. 
Different kinds of glass have different characteristics in this 
respect, and by combining different glasses and curves 
chromatic aberration is corrected. See Lens correction, 
page 132. 

It is in order to accomplish corrections of spherical and 
chromatic aberration, and other faults that several lenses 
are used in making up a projection lens. The different kinds 
of glass and different kinds of lenses combine to make the 
desired corrections. The condenser is uncorrected, hence it 
has spherical and chromatic aberration, as well as all the 
other faults inherent in uncorrected lenses. The chromatic 
aberration of the condenser causes the colored light which 
surrounds the spot, and its spherical aberration carries some 
of the color down into the center of the spot, thus injuring 
the brilliancy of the light projected to the screen. 

PROJECTION ANGLE.— See pages 20 and 255. 

PROJECTION DISTANCE.— See page 38. 

STANDARD FILM. —Shall be one and one-third inches 
wide, shall carry one picture to each four perforations, and 
sixteen pictures to each foot of film 





MANAGERS AND PROJECTIONISTS 


131 


CONDENSER.— See pages 25 and 164. 

LIGHT BEAM.— See page 32. 

Light RAY. —See page 32. 

WORKING DISTANCE.— See page 49. 

THE MECHANICS OF LENSES.— In order to understand 
the action of light through lenses it is necessary that the 
student get the “viewpoint.” This is a very difficult thing to 
do, mainly by reason of the fact that it is quite possible to 
view light action through lenses in more than one way, 
although regardless of which one of the possible views we 
may take the ultimate result is essentially the same. 

From the optical viewpoint each tiny pin point of the 
surface of a lens presents an entirely separate proposition 
from every other pin point, because of the fact that it pre¬ 
sents a different angle to the light, thus producing refraction 
slightly different from that of the point next adjoining if, 
and different from every other portion of the surface of the 
lens. 

One fundamental fact the student should get firmly fixed 
in his mind is that: 

Once a light ray has entered a lens at an angle to its sur¬ 
face, and has thus received its initial bending, or refraction, 
it will, if the glass be of even density, travel in a perfectly 
straight line until it reaches the opposite surface of the lens, 
where it re-enters the air, and in so doing receives its second 
bending or refraction. 

We thus see that, except for the slight variation in density 
of glass, the action of a lens is dependent wholly upon its 
surfaces, which fact should impress us with the imperative 
necessity that lenses have surfaces which are optically true. 

If a light ray enters and leaves a lens at exactly right 
angles to both surfaces of the glass there will be no re¬ 
fraction and the ray will pass straight through, but if it 
strikes the glass at an angle the ray will be bent or re¬ 
fracted. 

Thus, let us assume a pin point of light located on the 
optical axis of a simple lens. Rays from the light source, of 
course, diverge in every direction. The ray meeting the lens 
surface at the optical axis will meet the surfaces of the glass, 
both entering and leaving, at precisely right angles to its 
surface. In optical language, the ray will be “perpendicular” 
to the surfaces of the lens, hence there will be no refraction. 


132 


HANDBOOK OF PROJECTION FOR 


This particular ray will pass straight through, but the sur¬ 
face of the lens being curved at every point, the ray which 
strikes the lens %th or even l/100th of an inch from the 
optical axis of the lens will meet the glass at a slight angle. 
Hence the ray will be refracted, and the amount of refraction 
will be partly dependent upon the distance of the light 
source from the lens, since the distance of the light source 
from the lens of course controls the angle of the rays thereto. 
The same is true of the ray that meets the lens half an inch 
from its optical axis. In this case the ray will be refracted 
more than the one which meets the lens nearer to its 
optical axis. 

A very understandable illustration is found in the con¬ 
denser. Suppose the arc to be a pin point of light located 
3.5 inches from the surface of a 4.5 inch diameter lens. The 
ray which strikes the lens half an inch from its optical axis 
will not strike the glass at much of an angle, hence its initial 
refraction or bending will be slight, but the ray which strikes 
the lens near its outer edge will meet the glass at a heavy 
angle, hence its initial refraction will, by comparison, be very 
great. (See figure 28, page 128.) 

LENS CORRECTION. —All uncorrected lenses have both 
spherical and chromatic aberration. By means of a com¬ 
bination of different kinds of glass and positive and negative 
curvatures it is possible to correct lenses for both spherical 



Figure 30. 


and chromatic aberration. As a matter of fact, projection 
lenses are thus corrected. In this correction what is known 
as crown and flint glass are used. See Chromatic Aberration, 
page 130. 







MANAGERS AND PROJECTIONISTS 


133 


Those who wish further enlightenment on this matter, which 
has entirely to do with practical optical work, will find 
lengthy treatises on the subject in various optical works, 
which may be consulted at the public library. Also see “Optic 
Projection,” page 581 and Fig. 324. 

IMAGE FORMATION. —Assuming the lens in Fig. 30 to be 
free from spherical aberration, all rays emanating from any 
given point on light source X and striking the surface of the 
lens will be refracted in such manner that they will again 
meet at point Y, these two points being called the “conjugate 
foci” points of the lens. 

If light source X be located nearer the surface of the lens, 
point Y will automatically be moved farther away from the 
surface of the lens, and if light source X be placed near 
enough to the lens, point Y will finally be lost and the rays 
will leave the lens in parallel, or even in diverging lines. 

On the other hand, if light source X be moved farther away 
from the lens, point Y will automatically be brought closer 




to its surface. It is this law of optics which is brought into 
operation when the film image is focused on the screen by 
adjusting the projection lens—moving it nearer to or farther 
















134 


HANDBOOK OF PROJECTION FOR 


away from the film, which is, of course, exactly the same 
thing as moving the film itself nearer to or farther away 
from the lens. Assuming the - lens shown in Fig. 30 to 
represent the projection lens, X to represent the film, and Y 
the screen, if the lens be too far from, or too close to X, 
then the Y conjugate foci point will not be at point Y, and 
the rays will not meet or focus there, in explanation of which 
see Fig 36D. 

FOCAL LENGTH. —The focal length of a simple lens is 
the distance from its optical center to the image, when the 
image is in sharp focus and the object sufficiently distant to 
cause the lens to receive parallel rays of light. The focal 
length of a lens is determined practically entirely by the 
curvature of its surfaces. 

In Fig. 31, we see two lenses, one of which, A, has slight 
curvature, while the other, B, has rather heavy curvature. 
By reason of its slight curvature, the refractive power of the 
lens shown at A is not so great as is that of the lens shown 
at B. It will thus be seen that the heavier the curvature of 
the surface of lenses of this type, the shorter is their focal 
length. This is by reason of the fact that the heavier the 
curvature the greater will be the angle at which parallel rays 
of light will strike the glass, both on entering and leaving 
the lens, hence the greater the amount of refraction 
the rays will receive, and the nearer the lens they will be 
brought to an image forming focus. The surfaces of 



lenses used for pro¬ 
jection work, both 
condenser and ob¬ 
jective, are always 
the section of the 
surface of a true 
sphere. 


HOW LENS 
^ CURVATURE IS 
DETERMINED. - 


In Fig. 32 we are 
enabled to see how 
the curvature of an 
ordinary lens is de¬ 
termined. Looking 
at the measurements 
we see that the out¬ 
er circle is in- 


Figure 32. 

















MANAGERS AND PROJECTIONISTS 


135 


ches in diameter and the inner circle 6]/ 2 inches in diameter. 
Let us imagine the outer circle to represent the circumference 
of a glass ball, that we halve it and polish the flat sides of the 
discs of glass thus produced. We would then have two iy 2 
inch diameter, iy 2 inch focal length plano-convex lenses. 

If, on the other hand, we saw off a section 4 y 2 inches in 

diameter from the 
surface of the ball, 
and polish the flat 
side, we will have a 
4 x / 2 inch diameter iy 2 
inch focal length 
plano-convex lens. If 
the same thing be 
done with a glass 
ball 6y 2 inches in 
diameter the same re¬ 
sult would be had, 
except that in halving 
the ball we would get 
two inch diam¬ 

eter, 6J4 inch focal 
Figure 33. length lenses, and by- 

cutting off a section 
4 y 2 inches in diameter we would have a 4j4 inch diameter 
6y 2 inch focal length plano-convex lens. 

It will thus be seen that with a plano-convex lens the con¬ 
vex surface will always have the curvature of a circle, the 
diameter of which is equal to the focal length of the lens. It 
will also be noticed that the larger the diameter of such a 
lens the thicker it will be. 

The method of designing a meniscus lens is indicated by 
Fig. 33, in which the smaller circle represents the circle de¬ 
termining the outer or convex curvature of the lens, as in 
Fig. 32. But instead of a piano surface on the opposite side, 
as in the case of the plano-convex, the meniscus has a con¬ 
cave surface. We therefore determine the degree of curva¬ 
ture for the concave surface by means of the larger circle 
shown in Fig. 33. 

The designing of curves for a meniscus lens is an optical 
problem, entirely too involved for any except a man trained 
in such work. 

FOCUS. —At the risk of repetition we desire to impress 
upon the mind of the student the fact that unless the object 



136 


HANDBOOK OF PROJECTION FOR 


or light source be a pin point, a lens will not focus the light 
beam to a pin point. A lens is presumed to form an image, 
and an image always has area. The matter should be viewed 
thus: Rays emanate from each pin point of the object, or 
light source. (When projecting a light source, which is ex¬ 
actly what the condenser does, the light source becomes an 
“object/' within the meaning of that term as here used.) The 
rays from the particular pin point, and all other pin points 
of the object or light source, are picked up by a considerable 
area of the lens, or perhaps by its entire area, and the rays 
from each particular pin point of the object are refocused to 
a corresponding, though perhaps a magnified or reduced 
point in the image. That is what is meant by “focus.” It is 
illustrated in Fig. 30. 

A little study will enable the student projectionist to under¬ 
stand why he is unable to focus the condenser ray to a pin 
point. In the case of the condenser ray, the condenser is 
receiving rays from the entire area of the floor of the carbon 
crater, and is refocusing them to an image of the crater. By 
reason of the fact that the crater does not set square with 
the condenser (the lower part being farther away from the 
lens than the upper part, and the further fact that the un¬ 
corrected lenses used for con¬ 
densers set up spherical aberra¬ 
tion) the actual image of the 
crater will be focused over a con¬ 
siderable distance in the con¬ 
denser ray. Only a certain por¬ 
tion of the crater will therefore 
be in sharp focus at any one point 
in the condenser beam. Since the 
crater itself has considerable area, 
the image will have area, hence 
the beam cannot be focused to a point. 

PROJECTION LENS. —A projection lens is in fact a com¬ 
bination of four lenses, two of which are located at the end 
of the lens tube nearest the film. These two lenses are sepa¬ 
rated by a spacing ring by some manufacturers, but not by 
others, and the combination is commonly referred to as the 
‘ back factor” of the projection lens. The two other lenses 
located at the opposite end of the lens tube are cemented 
into direct contact with each other by means of Canadian 
Balsam, and are commonly referred to as the “front factor” 
of the projection lens. The front factor, usually being 



Figure 34, 





MANAGERS AND PROJECTIONISTS 


137 


cemented together, will, at a superficial glance, appear to 
be one thick lens. As a matter of fact, the combination con¬ 
sists of one negative lens and one double convex lens, as 
indicated in Fig. 34, which shows the detail of Gundlach- 
Manhattan lenses. 

It sometimes may happen that the balsam with which the 
front factor of the projection lens is cemented together 
will melt, thus causing the lens to have a sort of streaked 
appearance. Should this occur it will be necessary to send 
the entire lens back to the manufacturer to have the front 
factor recemented. It is possible to separate the lenses by 
heating them in hot water, but it will disturb the corrections 
of the lens. It is a job which can be properly done only by 
the manufacturer. 

KEYSTONE EFFECT. —Keystone effect and its accom¬ 
panying distortion cannot be removed or corrected by pro¬ 
jection lenses, specially ground or otherwise, it being the 
natural result of the difference in distance the rays at the 
top and bottom of the light beam must travel in order to 
reach the screen. See page 253. 

CLEANING LENSES.— It is essential to best results that 
the surfaces of the projection lens be kept scrupulously 
clean. Oil on the surface will cause very serious loss of 
definition in the picture, and even the faintest, almost im¬ 
perceptible finger mark will do the same thing, perhaps in 
lesser degree. An even distribution of an accumulation of 
dust particles from the air may not seriously affect sharpness 
of focus, but it sets up additional loss of light through reflec¬ 
tion. Hence from every viewpoint it is of great importance 
that the surfaces of the lenses be kept perfectly clean and 
highly polished. 

There are several patent preparations on the market for 
cleaning lenses, some of which are good. We believe, how¬ 
ever, that all the projectionist needs to keep his lenses in 
first class condition is half a pint of wood or denatured 
alcohol, diluted with half a pint of clean water. The com¬ 
bination fills a pint bottle, costs but a few cents, and if used 
economically lasts for a long time. 

Nothing but a perfectly clean chamois skin, or soft, per¬ 
fectly clean cotton cloths, such as old handkerchiefs, should 
be used for cleaning lenses. 

Lenses should be washed with a cloth saturated in the 
alcohol solution, and then quickly polished while still wet. 
It should be a part of the daily duty of the projectionist to 


138 


HANDBOOK OF PROJECTION FOR 


carefully examine the outer surfaces of his projection lenses 
and his condenser lenses, and to clean them if necessary. 
At regular periods the projection lens should be disassembled 
and the interior surfaces of the various lenses cleaned. In 
disassembling be very careful not to get the two rear lenses 
mixed because if they be wrongly replaced the corrections of 
the lens will be either ruined, or at least be so badly 
damaged that the lens will not give good definition. In 
replacing the rear combination get the side of heaviest 
curve toward the screen, and do not forget to replace the 
spacing ring, if there is one. 

The front (thick) lens combination should be placed in 
the mount, with its surface of greatest convex toward the 
screen. 

The guiding rule in reassembling a projection lens is to 
place all lenses with their greatest convex toward the screen. 

While the lens is disassembled, carefully examine the in¬ 
terior of its barrel and if at any point the black paint has 
worn off so that the metal shows, retouch it with lamp 
black ground in Japan, thinned with turpentine. Lamp black 
ground in Japan may be had at any first class paint store. 
It is known as coach painter’s black. Unless the interior of 
the projection lens be kept coated with non-gloss black 
there will be reflected light projected, which may fall out¬ 
side the screen proper. Cases have been known where the 
interior of the lens barrel reflected so much light from the 
above cause that a circle of light surrounded the entire 
screen. 

In reassembling, the lenses should be clamped snugly in 
their mounts, although it is advisable not to screw the ring 
down too tightly, remembering that in due time it must 
again be removed. 

Concerning this matter one lens manufacturer in an in¬ 
struction booklet on its lenses says: “In cleaning and 
assembling, first note whether the extension tube is at¬ 
tached to the front or rear end, so that you will replace it 
correctly. Clean both sides of the front combination, but 
do not remove it from its cell. To remove the retaining 
ring from the rear cell, press lightly on two sides of the 
ring with two fingers and unscrew it. Too much pressure 
will make it bind so that it will not turn. Clean inside sur¬ 
faces of the two lenses of the rear combination and replace 
in cell. Be careful that they are seated evenly, screw up 
the retaining ring just tightly enough to prevent them from 


MANAGERS AND PROJECTIONISTS 


139 


moving, then clean the outside surfaces. Note that the rear 
lens is convex on both sides, the flatter side being the out¬ 
side rear surface. The retaining rings should face toward 
the center. Reversing the cells will disturb the correction.” 

To remove grease or oil from the surface of a lens use a 
soft rag, free from grit, moistened with a little gasoline. 

Be careful when screwing the parts together to avoid 
crossing threads and do not screw up any joint very tightly. 

Do not use a hard, sharp tool to remove retaining rings. 
It may slip and scratch the lens. 

In reassembling Gundlach-Manhattan lenses follow Fig. 
34, which is a cut supplied by that company. 

REPAIRING LENSES. —Should one lens of a projection 
lens be broken or injured, it may be replaced, but in order 
to do this it is absolutely necessary that the complete lens 
be returned to its maker, with the broken or injured mem¬ 
ber. The broken element has no value whatever, but unless 
it is sent, there is danger that the focal length of the lens 
combination will be changed in the replacement. 

Odd lenses or combinations of lenses have absolutely no 
value. They cannot be utilized by lens makers to build 
complete lenses, except at greater cost than a completely 
new lens. The difficulty arises in matching other lenses to 
the old ones. In cases where just one lens of a combina¬ 
tion is broken the manufacturer can ascertain the exact 
formula for the broken lens by measuring the fragments. 

LENS APERTURE AND FOCAL LENGTH.— Lenses are 
not made with a free aperture (diameter of free opening) 
greater than half their focal length. For instance, a 4-inch 
focal length lens could not be made with a greater working 
aperture than 2 inches. In practice they are not even made 
that large. 

ORDERING LENSES. —In ordering projection lenses, give 
the following data: (A): Width of picture desired and dis¬ 
tance from the screen to projector aperture. If the lens is 
above center of the screen appreciably the latter measure¬ 
ment should be from midway between top and bottom of 
picture. (B) Make of projector. (C) Specify lenses with 
or without jackets. (D) If two lenses are ordered specify 
as to whether you want them matched or not. (E) If matched 
lenses are wanted and your projectors are new, it will not be 
necessary to give width of aperture, but if the projectors 
are quite old it will be best to have exact width of aperture, 


140 


HANDBOOK OF PROJECTION FOR 


measured with a micrometer caliper. This is especially im¬ 
portant if one projector be new and the other quite old. 

RANGE OF FOCAL LENGTH.— Projection lenses from 2 
to 8-inch E. F. are carried in stock by manufacturers. 

MATCHING LENSES. —Do not attempt to order a lens 
to match one you have by giving the focal length on the lens 
barrel. These focal length markings cannot be depended 
upon for close work. They are usually only approximate. 

If you have a lens and want one to match it you must send 
the lens to the manufacturer to be measured, or else give 
the manufacturer the precise width of the projector aperture 
as measured by a micrometer caliper, the exact distance from 
aperture to screen and the precise width of the light upon 
the screen when there is no film in the projector. 

Even with these precautions you cannot be certain, be¬ 
cause an error involving the smallest fraction of an inch may 
result in unsatisfactory results, if the error be made at the 
right place. If there is a keystone, the distance from screen 
to aperture must be measured at the same distance from top 
or bottom of picture that the width of picture is measured. 
Better send the lens. It is the only sure way. 

When lenses are purchased in pairs they are usually 
'matched by selecting lenses from stock. Suppose two lenses 
are wanted to project a picture of a certain width at a cer¬ 
tain distance. The dealer or lens maker finds by computa¬ 
tion that this requires a 5-inch E. F. lens. He tries one and 
finds it gives a picture a bit too large. He tries another and 
another until one is just right. He then, by a process of 
selection through tests, finds another which gives exactly 
the same size picture at that distance. 

Why is this, you ask? Why did not the 5-inch lens give 
what it was supposed to give? For the reason that lenses 
vary, and their markings are not accurate. A 4-inch E. F. 
projection lens may vary from 3.95 to 4.20 inches, according 
to the admission of one large lens concern. Exhibitors and 
projectionists should remember this when matched lenses are 
wanted. 

NOTICE.— The Gundlach Manhattan Optical Company 
marks the exact actual focal length of its projection lenses in 
the invoice sent to purchasers. This notation is in figures 
and in parenthesis. 

This bit of information should be carefully filed away in 
the projection room, because if a lens of that focal length 
is ordered later it will match the one you have. 


MANAGERS AND PROJECTIONISTS 


141 


LIGHT LOSS BY REFLECTION.— The Professors Gage 
set the losses due to reflection from the polished surface of 
each lens at as much as 4 to 5 per cent., or a total of 8 to 
10 per cent, for each lens, or plate of glass. They further 
remark that if the surface be not perfectly clean, or per¬ 
fectly polished, the light loss may amount to as much as 15 
per cent, of the total from each surface. Some authorities 
place the loss even higher, giving a minimum value of 6 
per cent per surface. 

In this connection the following valuable data was con¬ 
tributed by Dr. Hermann Kellner of the Bausch & Lomb 
Optical Com¬ 
pany, manufac¬ 
turers of pro¬ 
jection lenses, in 
the form of a 
paper read be¬ 
fore the Soci¬ 
ety of Motion 
Picture Engi¬ 
neers at its 
meeting in Day- 
ton, Ohio, Octo- 
b e r 12, 1920. 

This paper ap¬ 
pears in the 
Dayton trans¬ 
actions of the 
Society: 

“Losses of 
light in projec¬ 
tion lenses may 
occur for two 
reasons: 

“First, geometrical arrangement of power, distances, etc., 
sizes of lenses; 

“Second, physical reasons, material the lenses are made of, 
conditions of glass surfaces, etc. 

“It is the physical conditions with which we are con¬ 
cerned now. 

“When light strikes a border surface between two opti¬ 
cally different media, water and air, for instance, a part of 
the light enters the water and illuminates the bottom or the 
containing vessel, while another part is reflected back into 



Figure 35. 

























142 


HANDBOOK OF PROJECTION FOR 


the air. So is part of the sunlight which strikes a window 
passed into the room, while another part is reflected upon 
the street. The ratio of reflected to transmitted light de¬ 
pends upon the refractive indices of the media, as well as 
upon the finish of the surface. 

“The greater the difference in refractive index, the more 
light is reflected and the less light is transmitted. If we 

have two horizontal 
surfaces, side by side, 
one formed by water, 
the other of glass, 
and observe the 
amount of sunlight 
reflected, we will 
find the glass surface 
to be a more efficient 
reflector than the 
water surface, and at 
the same time the il¬ 
lumination inside the 
water will be greater 
than inside the glass. 

“The amount of re¬ 
flected light also 
changes with the 
angle of incidence. 

The more nearly per- 
anows tne curves tor tne loss oi ngnt in a J , , 

double convex lens of refractive index 1.51 at peildlCUlar the light 
and between the surfaces. source is to a sur¬ 

face, the less the 

amount of light reflected. From this it is evident that the 
conditions for passing the greatest amount of light become 
most favorable when the refractive index is as low and the 
angle of incidence as small as possible. Remembering that 
the angle of incidence is the angle between the direction of 
the ray of light and the perpendicular at the point of incident, 
we see that the nearer the ray of light is perpendicular at the 
point of incidence the smaller is the angle of incidence. 

“The action of a lens depends on the refractive index of 
the material it is made of. To get any lens action at all, 
the refractive index has to be greater than that of air, the 
value of which is set at 1.00. We therefore shall always have 
a certain loss of light when it passes through a lens sur¬ 
face. The amount of this loss is determined by means of a 






























MANAGERS AND PROJECTIONISTS 


143 


formula which was derived by Fresnel, the famous French 
mathematician and optician, 
incidence the following equa¬ 
tion : 

( n —1) 

I — I 1 =-2 

(n+1) 

Wherein I is the amount of 
light falling upon the surface; 

I 1 the amount of light trans¬ 
mitted by the surface; and n 
the refractive index of the 
medium. The difference I — 

I 1 is the loss of light at the 
refracting surface. The curve 
in Fig. 35 shows, for refrac¬ 
tive indices varying from 1.0 
to 1.8, the intensities of the 
reflected and transmitted light. 

“The amount of variation in 
loss of light with variation 
in the angle of incidence is 
set forth in the following 
table, in which it is assumed 
that the light is unpolarized, 
an assumption which satisfactorily represents practical con- 


ditions : 

Table 6A 


Angle of 
Incidence 

Per Cent. 

Per Cent. 

Degrees 

Crown 1.51 

Flint 1.61 

0 

Loss 4.13 

Loss 5.46 

30 

“ 4.28 

5.64 

60 

“ 9.08 

“ 10.69 

70 

“ 17.29 

“ 18.97 

80 

“ 38.92 

“ 40.30 

90 

“ 100.00 

“ 100.00 


Caution Note. —“Crown 1.51” and “Flint 1.61” refer to re¬ 
fractive index of those glasses. 

“The refractive indices of the glasses used in projection 
lenses, which are crown and flint, vary from about 1.51 
to 1.61. 

“From table 6A we learn that the loss of light per surface 
for perpendicular incidence is 4.13 per cent, for crown glass 


He found for perpendicular 



Shows the curves for the loss of 
light in a double convex lens of 
refractive index 1.61, at and be¬ 
tween the surfaces. 




























HANDBOOK OF PROJECTION FOR 


144 


the refractive indice of which is 1.51. Whereas for flint glass 
the refractive indice of which is 1.61 the loss amounts to 
5.46 per cent. 

“The angle under which light rays strike the surfaces of 
a projection lens varies from 0° to about 30°, and fortunately 
for the simplicity of this discussion the variation of the 

loss within these 
angles is negligi¬ 
ble, as may be 
seen in the table. 
We may there¬ 
fore say that the 
loss of light per 
surface on a 
crown glass lens 
amounts to 4.2 
per cent., and on 
a flint glass lens 
it is 5.5 per cent. 

“The refractive 
index of Cana¬ 
dian Balsam is 
a pproximately 
equal to that of 
crown glass, 
therefore if a 
crown lens of 
1.51 and a flint 
lens of 1.61 be 
cemented to- 
Shows the curve for the loss of light in a cemented gether, the loss 
doublet consisting of a lens with refractive index , 

1.51 and another lens with a refractive index 1.61 ^y renection at 
at and between the surfaces. a cemented sur- 

face is very 

much smaller than at surfaces bordering on air. The reflective 
index of Canadian Balsam being practically the same as 
that of crown glass, no loss is incurred in the passage from 
the crown glass lens into the layer of balsam, while between 
the balsam and the flint glass the difference amounts to only 
0.1 per cent., which means the total loss is almost negligible. 

“For a number of glass surfaces in air, each having about 
the same loss by reflection, the total loss may be arrived at 
by using the compound interest formula. If the loss, p, for 










































MANAGERS AND PROJECTIONISTS 


145 


one surface is represented as a fraction of the initial in¬ 
tensity, the loss for k surfaces will be 1—(1—p)k. 

“The loss by absorption depends on the nature of the 
glass and on the thickness of the lenses. Good crown glass 
will not absorb more than 0.5 to 1 per cent, per centimeter 
thickness, while flint glass of 1.61 refractive index will run 
a little higher, from 1 to 1.5 per cent, per centimeter. 

“The lighter varieties of flint glass, of indices between 
1.54 and 1.61, have absorptions between these limits, while 




A B 

Figure 36C, 

the absorption of poor glasses runs as high as 3 and 4 per 
cent, per centimeter. 

“Considering a crown glass lens of an average of 5 mm. 
thickness, the losses by reflection and absorption total up 
as follows: At first surface 4.2 per cent., by absorption .5 
per cent., at last surface 4 per cent., or a total of about 9 
per cent, per lens. 

“With a flint lens of 1.61 refractive index we obtain the 
following data: Loss at first surface 5.5 per cent., by absorp¬ 
tion .5 per cent., at last surface 5.2 per cent., or a total of 
about 11 per cent, per lens. 

“For a cemented lens consisting of cemented crown and 
flint elements we find 4.2 per cent., .5 per cent., .1 per cent., 
1 per cent., 5.2 per cent., or again, a total of about 11 per 
cent. Figures 36, 36A and 36B represent these conditions 
graphically. 













































146 


HANDBOOK OF PROJECTION FOR 


“In this, way it is easy to form an opinion as to the losses 
by reflection and absorption in any combination. In gen¬ 
eral it is safe in forming an estimate to assume the total 
per single lens, or per combination of cemented lenses, as 
they occur in projection lenses, at about 10 per cent. 

“If the workmanship and material are approximately the 
same, and no difference exists in the geometrical arrange¬ 
ment, diaphragming, etc., of the lenses, the amount of light 
passed through is very nearly the same in all lenses that 
have the same number of reflecting surfaces. 

RESULT OF DIRTY LENSES. — ‘A very important factor 
in the performance of a lens is the condition of its surfaces. 
Scummy and dust-covered lenses give gray pictures, with no 
contrast, exactly in the same way that photo lenses will not 
take good pictures if dispersed light from finger-marks on 



the lens is allowed to reach the plates. It is therefore of 
the utmost importance that in comparative tests the lenses 
be perfectly clean. 

“I may mention briefly the fact that there exists a con¬ 
dition of lens surfaces which is helpful in the way of re¬ 
ducing the amount of reflected light and increasing the 
amount of transmitted light. Such surfaces have an 
iridescent appearance caused by chemical action. It had 
been discovered accidentally in process studios that such 
lenses allow shorter exposures. Upon investigation it was 
found that the amount of transmitted light actually had been 
increased. Unfortunately such action takes place for the 
most part on glasses which have comparatively great absorp¬ 
tion co-efficients, and not generally used for projection 
lenses. Any thought of reducing losses in projection lenses 








MANAGERS AND PROJECTIONISTS 


147 


by these means will probably have to be dismissed, although 
the amount of loss by such treatment can be reduced by as 
much as 50 per cent. 

“In conclusion I may say that all the statements made 
above are borne out by practical tests, not only in compara¬ 
tively simple combinations like projection lenses, but also 


/955EMBL Y OPT/YS 



in the most complicated apparatus like range finders, sub¬ 
marine periscopes, etc.” 

(Not e —We have made a few changes in Dr. Kellner’s 
language to lessen his technicality for our readers, but his 
meaning has in no degree been altered.—Author.) 

PROJECTION LENS DIAMETER.— For reasons which 
will be explained in later pages, the diameter of the pro¬ 
jection lens is a matter of large importance. Under condi¬ 
tions where the amperage is high and the working distance 
of the projection lens long a small diameter objective means 
heavy loss in efficiency—waste of light—as well as uneven 


BSSSWBL Y OPT/CS 



Figure 36EE. 


















































































148 


HANDBOOK OF PROJECTION FOR 


illumination of the screen, with consequent loss in “depth” 
in the picture itself. On the other hand, it may be accepted 
as fact that the small diameter objective makes for improve¬ 
ment of the picture, gives much greater depth of focus— 
an important matter indeed where there is considerable 
angle to the projection—and in general sets up a better con¬ 
dition with regard to the revolving shutter. It follows that 


/)S$£rt3L y OPT/CS 



DESIGN 

POCO S 

QU/?/eT£e S/Z£ 

4’to 

SMJ?£/./7£ 


Figure 36F. 


any diameter greater than that necessary to accommodate 
the actual picture bearing light beam is not only undesirable, 
but distinctly bad. 

We might, however, here repeat that it is impractical to 
make projection lenses of greater free diameter than half 
the focal length (E. F.) of the lens. This is a limitation 
which often causes a bad condition, especially in the shorter 
focal length lenses because, except in the case of very short 
E. F. lenses, only two diameters are made in practice. 
Whether it is practical to make all projection lenses up to 
5-inch with a free diameter equal to half the E. F. of the 
lens or not, we do not know. However, if it can be done 
without sacrificing any valuable quality of the lens it cer¬ 
tainly should be done. 

DISTORTION. —Projectionists should carefully test their 
projection lenses for distortion. This may readily be done. 
First secure a perfectly flat piece of mica, commonly known 
as isinglass, three or four inches in length. Trim it to the 
exact width of a film and then, using a coarse needle, 
scratch straight lines on the surface of the mica, checker¬ 
board fashion, as per Fig. 36C. 











































MANAGERS AND PROJECTIONISTS 


149 


Having done this, place the mica over the projector aper¬ 
ture and close the film gate, being careful that the mica 
lies perfectly flat over the aperture, just as the film would 
lie. Next, raise the fire shutter and project the lines on the 
surface of the mica to the screen, and with a tightly 
stretched cord, test the lines on the screen to see that they 
are perfectly straight. At A, Fig. 36C, the lines are straight, 
hence there is no distortion. At B there is what is known as 
“barrel distortion,” which amounts to a curvature of the 
lines. The lens which projects B is not a good lens, whereas 
the lens which projects A is perfect, insofar as has to do 
with distortion. 

CAUTION.—Lines on the mica need not be perfectly square 
with each other, but each line must be perfectly straight. 

FOCUSING. —The objective must focus all rays of light 
emanating from a given point of the film to a corresponding, 
though magnified, point on the screen. 

As has already been set forth, the film represents one 
conjugate foci point of the objective and the screen the 
other. As you all know, if the distance of the objective from 
the film be in the slightest degree altered by means of the 
focusing screw, the definition of the picture on the screen 
is altered. The reason for this is diagrammatically repre¬ 
sented in Fig. 36D. 



Here A is the film, B the objective, and 2 the screen posi¬ 
tion, with the picture out of focus because of the fact that 
lens B is too far from film A. The rays emanating from 
points in film A are thus focused at 1 instead of at 2. Be¬ 
tween B and 1 the rays converge until they finally meet at 









































150 


HANDBOOK OF PROJECTION FOR 


1, but having met at 1 they cross and continue in straight 
lines, diverging, so that at position 2 each pin point of the 
film is represented by a bundle of rays, or a circular spot of 
light. Now, if we move lens B just a little closer to film A, 
the point of focus will then be at 2, instead of at 1. A 
study of this diagram should inform the projectionist as to 



/=OCl/S 

///?//" 5/Z£ 

3 // ' 



Figure 36FFF. 


exactly what takes places when he focuses the picture on 
the screen. 

“DOCTORING” LENSES. —The author has often been 
asked this question: “Can the E. F. of a lens be altered by 
shortening or lengthening its barrel in such a way that the 
distance between the back and front factor will be changed”? 

This question must be answered both yes and no. The thing 
may be done, but only at the expense of ruining the lens, 
insofar as concerns its ability to do high class work. 

PROJECTION LENS AND PICTURE SIZE.— The question 
is often asked, “Can a given projection lens be used to pro¬ 
ject a picture at different distances”? The answer is, yes. 

But the same objective will not project the same size pic¬ 
ture at different distances. 

If the distance be made less, the picture will be smaller, 
and vice versa. Changing the distance of projection will 
also alter the working distance of the lens—distance from 
back factor to film. The shorter the distance between the 
lens and the screen the further the lens must be from the 
film, and vice versa. 

The light beam diverges on its way from the projection 
lens to the screen. It is easy to figure how much change in 














































MANAGERS AND PROJECTIONISTS 


151 


size of picture will be accomplished by moving the screen 
a given distance nearer to or further away from given lens, 
since the divergence of the ray emanating from any given 
projection lens is a fixed quantity, and does not alter. See 
“Same Lens, Different Distance,” page 154. 

MEASURING LENSES. —It is not only desirable, but 
essential that the projectionist understand how to determine 
the focal length of the various lenses he is called upon to 
handle, with at least a reasonable degree of accuracy. 

Condenser lenses, being uncorrected and containing con¬ 
siderable spherical aberration, cannot be measured with any 
great degree of accuracy by following method but the 
focal length of plano-convex condenser lenses may never¬ 
theless be obtained with sufficient accuracy for practical 
purposes. Select a room with only one window, or else 
darken all the windows in a room but one, leaving this one 
open. On the wall opposite this window pin a sheet of 
white writing paper. Hold the lens to be measured in front 
of the paper screen thus established,. with its flat side 
toward the screen, and carefully focus some distant object, 
such as a building or tree, on the paper screen. Be careful 
to hold the lens as nearly as possible square with the screen. 
Having focused the object selected as sharply as possible, 
measure the exact distance from the flat side of the lens to 
the screen, after which reverse the lens so that its curved 
side is toward the screen, focus the same object and again 
measure the distance from the flat side of the lens to the 
screen. Add these two measurements together and divide 
their sum by two. 

This result will be near enough to focal length of the lens 
for practical purposes. 

CAUTION.—In the foregoing it is essential to accuracy 
that the object focused be not less than 100 feet away, be¬ 
cause of the fact that the focal length of the lens is the 
distance from its optical center at which it will focus parallel 
rays of light, and with less than 100 feet the rays entering 
the lens from a point on any object cannot be said to be 
parallel. 

It is, however, possible to secure fairly accurate results by 
focusing an object which is only 50 feet away, and no great 
error will result even if the object fixed be only 15 or 20 
feet away. But always focus an object 100 or more feet 
away if it is possible to do so. 

For example, suppose the measurement with the flat side 


152 


HANDBOOK OF PROJECTION FOR 


of the lens to the screen to be 6 inches, and the second 
measurement, with the curved surface toward the screen, 7 
inches. Then, 6+7=13, and 13^-2=6H, hence the focal length 
of the lens is 6 l / 2 inches. 

A bi-convex condenser lens may be measured the same as 
the plano-convex, except that a single focusing is sufficient. 
The measurement should be from the center of the lens to 
the screen. 

The Meniscus bi-convex cannot be measured in the same 
manner as a plano-convex, because its optical center lies 
outside the lens. 

The motion picture or stereopticon projection lens has 
these two distinct measurements: (1) the “working distance,” 
which is the distance from the object (film or slide) to the 
first surface of the first factor of the lens when the image on 
the screen is in sharp focus, and (2) the “equivalent focus” 
(E. F.), which is one-fourth the distance from an object to 
its image when the object is focused by the lens being 
measured and the image and object are of the same size. 

The working distance of the motion picture projection lens 
is of great importance to the projectionist, in that it has 
directly to do with necessary lens diameter, as will be set 
forth in figure 47, page 182. 

The equivalent focus of the motion picture projection 
lens is the factor used in ordering lenses to project a given 
size picture at a given distance. 

MEASURING WORKING DISTANCE.— To measure the 
working distance of a projection lens, place it in the pro¬ 
jector, thread in a film and focus the picture sharply on the 
screen. Remove the film, and running a rule through the 
projector aperture, measure the distance from the aperture 
plate (film plane) to the first surface of the projection lens. 
This measurement will be the “working distance” of the 
lens, wrongly referred to as the “back focus.” See “Back 
Focus,” page 21. 

MEASURING EQUIVALENT FOCUS.— The equivalent 
focus (E. F.) of a projection lens may be measured accurate¬ 
ly as follows: Remove the projector mechanism and in the 
position occupied normally by the projector aperture, 
mount a sheet of metal in which an opening about .75 of an 
inch square has been cut. Next support the lens to be 
measured at a distance about twice its supposed E. F. on 
what would be the screen side of the aforesaid opening. 
Then, with the light projected through the opening in the 


MANAGERS AND PROJECTIONISTS 


153 


usual way, hold a small screen, preferably of a dull black 
or very dark non-gloss color on the screen side of the lens. 
Move lens and screen until the image of the opening on the 
screen is precisely the same size as the opening itself, where¬ 
upon one-fourth the distance from aperture to screen is the 
exact E. F. of the lens. 

To obtain this measurement properly what is known as 
an “optical bench” is necessary. We do not submit it as 
having much actual value to the projectionist, but merely 
for the sake of completeness. 

TO MEASURE ANY LENS. —The following method of lens 
measurement was supplied by John Griffith. It may be used 
to measure the focal length of any simple lens, such as a 
plano-convex, bi-convex or meniscus, or it may be used to 
measure the E. F. of compound lenses, such as projection 
lenses. 

To apply it, two things are necessary. The EXACT dis¬ 
tance lens to screen, and a stereo slide on which is an 
opaque mark precisely .5 of an inch in length. 

As to the slide, it may well form a permanent part of the 
projectionist’s tool outfit. It may be made in several ways, 
the easiest of which is to cut a piece of thin metal precisely 
.5 of an inch in length, binding the same up between two 
cover glasses. 

Another way is to make a scratch mark on a cover glass. 
A third way is to cut a slit in a metal slide, the latter being, 
of course, harder to make, but once it is finished it is in the 
nature of a permanent tool. However you may choose to 
make your test slide, be certain the mark is exactly one- 
half inch long, running, of course, horizontal—lengthwise on 
the slide. 

Next it is necessary to measure the exact distance from 
the lens to that part of the screen to which the line will be 
projected, the latter because of the fact that under some 
conditions there is a decided difference in distance from lens 
to different parts of the screen, also a difference in length 
of the projected line. This measurement must be reduced 
to inches. We would suggest that the distance from screen 
to inside wall of projection room at a point midway of the 
vertical height of the lens port be made a permanent part of 
the projection room records. It will then be a simple mat¬ 
ter to add to that measurement the distance from that point 
to the lens. 

Having the distance measurement and slide, project the 


154 


HANDBOOK OF PROJECTION FOR 


latter to the screen with the lens to be measured (a con¬ 
denser lens may be used for a projection lens, hence you can 
measure condenser lenses by this method)- and measure the 
exact length of the projected line on the screen. The rule is: 

As many times as .5 is contained times into the length of 
the projected line, measured in inches, the focal length of 
the lens, if it be a simple lens, or the E. F. of the lens, if it 
be a compound lens, such as a projection lens, will be con¬ 
tained into the distance of projection (lens to screen) meas¬ 
ured in inches. 

For example: The projected line, or mark, is found to 
measure 7 feet 8.3 inches, or 92.3 inches. The distance from 
the lens to the screen (distance of projection) is 100 feet, 
or 1,200 inches. We then have 92.3=.5=184.6 (dividing by 
.5, or y 2 , is exactly the same as multiplying by 2) and 
1200=184.6=6.5 plus a small fraction. Therefore our lens is 
a trifle over 6.5 inch focal length, if a condenser lens, and a 
bit more than 6.5 E. F., if a projection lens. 

EQUIVALENT FOCUS AND PICTURE SIZE.— The width 

of picture any projection lens will project at a given distance 
is dependent upon the E. F. of the lens. The shorter the E. F. 
of the lens the wider the picture it will give at a given dis¬ 
tance of projection, thus: A 4 inch E. F. projection lens will 
project a much wider picture at sixty feet than will a 6 inch 
E. F. lens. 

SAME LENS, DIFFERENT DISTANCE.— The same pro¬ 
jection lens may be used to project at different distances, but 
the resultant picture will vary in size directly as the distance 
of projection. If the size of the picture a lens projects at 
a given distance is known, the size it will project at any 
other distance may be computed, thus : 

Suppose a lens projects a sixteen foot picture at seventy 
feet. Reducing the size (width is always meant when pic¬ 
ture “size” is named with only one dimension given) to inches, 
we find the picture to be 16x12=192 inches wide. Since 
the distance to the lens is 70 feet, it follows that the ray 
from the lens spreads 192=70=2.742857 inches per foot. We 
have then only to multiply any desired distance of projection 
by 2.742857 to know precisely what size picture that lens 
will give at that distance. 

CALCULATING NECESSARY E. F. FOR PICTURE 

SIZE.— To compute the required E. F. of lens to project a pic- 


MANAGERS AND PROJECTIONISTS 155 

ture of given size (width) at a given distance, proceed as 
follows: 

Measure the width of aperture of your projector accurate*- 
ly (if it is a stereopticon lens, then the standard slide mat 
width, 3 inches, is used) by means of an inside caliper, though 
if the projector be of late model we may take the aperture 
width at .90625 (29/32) of an inch with assurance of pretty 
close accuracy. Next measure the exact distance from the 
center of the lens barrel to the screen. Multiply the distance 
from the lens to the screen, in feet, by the width of the aper¬ 
ture, in fractions of an inch, and divide the result by the width 
of the picture you desire, in feet. 

The result will be the E. F. of the lens required to project 
a picture that width. It will be as close to it as you or any 
one else can get by figuring. If the lens itself is accurate 
as to E. F., the result also will be accurate. 

For instance : Suppose we desire a fifteen foot picture at 
sixty feet. The projector aperture is found to be .90625 
(29/32) of an inch wide—the new standard. We first multiply 
the distance from the screen, in feet, by the width of the 
aperture, .90625, which gives us 54.3750. Dividing this by 
the width of the desired picture in feet we get 3.625. We 
would therefore require a lens of 3.625 inches E. F. to pro¬ 
ject a picture exactly 15 feet wide at exactly 60 feet. 

It would probably be impossible to find a lens marked 
exactly this focal length. The most practical method is to 
determine the width of the picture you want and the exact 
distance from the lens to the screen, supplying this data to 
the lens dealer. He will probably be able to select a lens 
from his stock which will meet your requirement. 

The stereopticon lens is figured in exactly the same way, 
except that instead of measuring the aperture width we 
accept 3 inches as the standard slide mat width—the slide 
mat being, in this case, the aperture. 

For the benefit of our readers we append the formula by 
means of which certain other factors may be figured: 

The size of the image which a lens of given E. F. will 
project at a given distance may be found by multiplying the 
difference between the distance lens to screen and the focal 
length of the projection lens (E. F.) by the width of the 
aperture, and dividing the product by the E F. of the lens. 
For example, let L equal the projection distance, 40 feet 
(480 inches); S the slide mat (3 inches), and F the E. F. 
of the lens, which we will assume to be 12 inches. We then 


156 


HANDBOOK OF PROJECTION FOR 


S (L ~ F) 

have the formula d =- in which d is the width of 

F 

the image in feet. Substituting for the letters their known 
3 (480—12) 

value we have: d =-=117 inches or 9.75 feet; 

12 

that being the width of a picture a 12-inch E. F. stereopticon 
lens will project at 40 feet, provided always that the slide 
mat be exactly 3 inches wide. If, however, the mat be more 
or less then 3 inches wide, then the picture will be more or 
less than 9.75 feet wide. The image size a motion picture 
projection lens would give at a given distance may be fig¬ 
ured in the same way, using the exact width of the projec¬ 
tor aperture instead of the slide mat width. 

If we know the size of the image, the width of the aperture 
and the E. F. of the projection lens, we may figure the dis¬ 
tance to the screen as follows: 

F (d+S) 

L =- 

S 

Suppose, for instance, we have a 12-inch E. F. stereopticon 
projection lens, and want a picture 117 inches wide. Sub¬ 
stituting figures for the above formula we have 
12 (117+3) 

L =-= 480 inches or 40 feet. 

3 

We would therefore be obliged to place the screen 40 feet 
from the lens in order to get out the 117-inch picture desired. 

LENS QUALITY. —In the past the author has advised the 
installation of high grade projection lenses, meaning by “high 
grade” an expensive, highly corrected lens. We still believe 
firmly in high quality lenses, but are convinced that some of 
the manufacturers of lenses in the United States are now 
producing projection lenses quite good enough for all prac¬ 
tical purposes, insofar as quality be concerned. The mount¬ 
ings of these lenses are excellent and the resultant image 
is very good indeed. With regard to anastigmat projection 
lenses, we believe they are only desirable in comparatively 
short focal length lenses. An anastigmat projection lens of 
long or even moderately long focal length does not seem to 
present any particular advantage. 

All projection lens manufacturers of prominence were in¬ 
vited to submit such data as would be of benefit to the users 






MANAGERS AND PROJECTIONISTS 


157 


of this book. The Koll-Morgan Optical Company, Brooklyn, 
New York, submitted the excellent data found in Figs. 
36E to 36FFF. From these excellent drawings all necessary 
data may be had. 

Under “Assembly” the lenses are shown mounted and un¬ 
der “Optics” we see the lenses of each lens unmounted, to- 
together with the dimensions in millimeters. It will be 
observed that the Snaplite lenses have five diameters, and 
that they range from 2.5 to 11-inch E. F. They are very 
well mounted and by comparison with some other makes of 
projection lenses are very highly corrected. They have the 
approval and indorsement of the Projection Department of 
Moving Picture World and of the author of this book. 

BAUSCH & LOME LENSES.— The Bausch & Lomb 
Optical Company, Rochester, New York, manufactures pro¬ 
jection lenses. 

The company 
supplied very 
complete data 
concerning 
same. The 
Bausch & 

Lomb lenses we 
have found to 
be highly cor¬ 
rected, well 
made and well 
mounted. They 
are cordially 
commended for 
all conditions to 
which their 
diameters are 
suited. The il¬ 
lustrations show 
clearly the as- 
semblage of 
lenses and their relation to each other, while the tabulated 
data gives all necessary information as to both outside and 
free diameter. 

It will be noticed that in series O and I lenses of the 
same E. F. may be had in two different diameters. We 
could hardly imagine the condition where the O diameter 


SERIES I SERIES 0 




Figure 36G. 

B. & L. Lenses—Exactly one-half size of actual 
lens. 





























158 


HANDBOOK OF PROJECTION FOR 


would be better, unless it be in the case of a heavy angle 
projection which compelled great depth of focus. 


0zrj3/£r&: 1/ 



b- 


Oor£>/D£ V/Arterea- 


Figure 36GG. 

B. and L. lenses, series 11, exactly one-half size of actual lens. 


LENS TABLES OF NO PRACTICAL VALUE. —Nearly all 
lens and projector manufacturers put out lens tables pur¬ 
porting to give the size of image a lens of given E. F. will 
project at a given distance. We did not incorporate these 
tables in this work because we do not regard them as having 
any practical value. In the case of the stereopticon, slide 
mat widths vary so much that the results from such tables 
are little more than guesswork. In the case of the motion 
picture the average exhibitor or projectionist wants a picture 
of exactly the size he has decided upon, at an exactly pre¬ 
determined distance, and for such accuracy he cannot rely 





































MANAGERS AND PROJECTIONISTS 159 

upon tables. Hence the tables are not, we feel, a desirable 
thing. 

Note: To change mm. measurements to inches multiply 
same by .03937. 


SERIES 0. SERIES I. 




Outside 

Inside 


Outside 

Inside 



Diam. 

Diam. 



Diam. 

Diam. 

No. 

E.F. 

mm. 

mm. 

No. 

E.F. 

mm. 

mm. 

1 

4" 

38.0 

36.0 

10 

4" 

46.0 

44.0 

2 

414" 

tt 

(( 

11 

4%" 

it 

it 

3 

4 J4" 

it 

it 

12 

4 y 2 " 

it 

it 

4 

4%" 

it 

it 

13 

4%" 

ft 

it 

5 

5" 

H 

it 

14 

5" 

tt 

a 

6 

5 %" 

tt 

tt 

15 

5 %" 

it 

it 

7 

5 J A" 

it 

it 

16 

5 W 

if 

tt 

8 

5%" 

tt 

it 

17 

5%" 

it 


9 

6" 

it 

it 

18 

6" 

it 

«• 





19 

6%" 

ft 

a 





20 

(V/ 2 " 

tt 

a 





21 

6%" 

tt 

tt 





22 

7" 

tt 

it 





23 

7 l A" 

tt 

it 





24 

8" 

tt 

a 




SERIES II. 






Front Combination 

Back Combination 

No. 

E.F. 

Diameter. 

Diameter 

Diameter 

Diameter 



Outside 


Inside 

Outside 

Inside 

40 

5%" 

64.0 


62.0 

49.0 


47.0 

41 

6" 

it 


if 

11 


(( 

42 

o%" 

tt 


ft 

t« 


it 

43 

6H" 

11 


if 

64.0 


62.0 

44 

6%" 

it 


tt 

tt 


it 

45 

. 7" 

tt 


ft 

tt 


it 

47 

7%" 

tt 


tt 

tt 


tt 

49 

8" 

tt 


tt 

ft 


tt 

51 

8V 2 " 

it 


tt 

i i 


tt 

53 

9" 

tt 


tt 

ft 


a 


Dimensions of Bauscli & Lomb Motion Picture Lenses, compiled for 
F. H. Richardson. 


THE MAN WHO GETS AHEAD IS 
THE MAN WHO REALIZES HOW 
VERY LITTLE HE KNOWS COM¬ 
PARED WITH WHAT THERE IS 
TO KNOW. 








160 


HANDBOOK OF PROJECTION FOR 


Practical Projection Optics 

T HE optical system or optical train of the motion picture 
projector is made up of two entirely separate elements, 
or lens systems, which are joined together in such a 
way that one system (the projection lens) receives at one of 
its conjugate foci points the magnified and more or less out 
of focus image of the light source projected by the other 
system, the condenser. 

The optical train of the projector consists of the con¬ 
denser, (A) the office of which is to pick up as great a num¬ 
ber as possible of the diverging rays from the light source, 
refract them into converging rays and concentrate them into 
what is known as the “spot” at the aperture^of the pro* 
jector, and (B) the projection lens, the office of which is to 
pick up the film image illuminated by the concentrated rays 
from the condenser and project it to a focused image upon 
the screen. 

The joining of these two optical systems is no difficult 
matter if we disregard the item efficiency, but to join them 
in such way that they will work together with the greatest 
possible degree of efficiency is somewhat intricate, and 
in some conditions met with an almost impossible problem. 
Yet, unless the two lens systems are made to work together 
with the least possible loss, the waste in light, which means 
waste in electric power, may and probably will be a very 
serious matter, indeed. 

We do not believe the optical system of the modern pro¬ 
jector can be judged by ordinary optical standards, because 
of the fact that the conditions under which the lenses must 
work are themselves, in almost every particular, highly 
abnormal. In the case of the condenser the heat is excessive 
under any condition, and when the amperage mounts to 80, 
90, 100, and even in some extreme cases higher, a condition 
is set up which calls for special treatment. In the case of 
the projection lens, it may, under some conditions, receive 
along with the film image it is to project to the screen, a 
more or less in focus image of the floor of the electric crater, 
or Mazda filament projected by the condenser system, and 
unless the projectionist very thoroughly understands his 


MANAGERS AND PROJECTIONISTS 


161 


business it is more than likely also to receive only a portion 
of the light passing through the aperture, which means an 
unevenly illuminated image on the screen, and in addition to 
all this it will receive more or less stray light reflected from 
the edge of the aperture. Nor is this all the story of the 
difficulties of the motion picture projection lens, because due 
to manufacturing limitations, and the further fact that it 
must work in conjunction with the revolving shutter, its 
diameter is necessarily limited. Its diameter is also, to an 
extent, limited by the further fact that too-large diameter 
makes for lack of depth of focus in the screen image, which 
latter is a very important item indeed, if the projection lens 
be considerably above, or to one side of the center of the 
screen. 

In the following we shall do our best to convey a clear 
understanding of practical projection optics, which is, we can 
assure you, no easy task. 

The collector lens element of the condenser (collector lens 
is the one next the arc) must pick up the light emanating 
from the light source, which approaches the lens in diverging 
rays, see Fig. 36H. 

THE LAW OF LIGHT.— Light diminishes in intensity as 
we recede from the source of light. If the luminous source 
be a point, then the intensity diminishes as the square of 
the distance increases. If we call the quantity or amount of 
light received by a certain given area at the distance of one 
foot 12 C. P., then at a distance of 2 feet its intensity would 
be %th of 12, or 3 C. P., and at a distance of 3 feet it would 
be l/9th of 12, and at a distance of 10 feet it would be 1 / 100th 
of 12, and so on. This is the true meaning of the law, which 
reads: 

With an open light source, light intensity varies inversely 
as the square of the distance from its source. 

This law has its base in the fact that light is propagated, 
or travels in straight lines, and naturally those lines are 
diverging—separate from each other as they go forward. 
You may prove the law as follows: Place a light source, 
which may be an incandescent globe, though the law holds 
strictly true only with point light sources, at a distance of 
nine feet from a white wall. Hold a cardboard six inches 
square at a distance of exactly 2.25 feet from the light source, 
which is one-fourth the distance from light to screen, and 
you will find the area of the shadow of the cardboard which 
is cast upon the wall to be sixteen times that of the card- 


162 


HANDBOOK OF PROJECTION FOR 


board itself. It therefore follows that the amount of light 
falling upon one square inch of the cardboard would be 
sixteen times as much as would be the light falling upon a 
similar area of a screen located four times as far away from 
the light source. The operation of this law and the practical 
effect of distance of crater from face of collector lens is 

very clearly 
shown in Fig. 
36H, in which F 
is an ordinary 
4 l / 2 inch diam¬ 
eter plano-con- 
v e x collector 
lens, having a 
free opening of 
4^4 inches, its 
face located 2 y 2 
inches from the 
center of the 
crater floor. 

With the cra¬ 
ter thus estab¬ 
lished, it re¬ 
quires no unus¬ 
ual power of 
discernment to 
understand that 
the lens will re- 
' Figure 36H. ceive all light 

rays within the 

space bounded by lines A—B. That much may be very 
readily understood. 

Remembering that once the light rays have left the source 
(crater floor) they travel in absolutely straight lines to in¬ 
finity, it is readily seen that if we move lens F back to the 
position occupied by lens C it cannot and will not receive as 
great an amount of light as it did in the first position. In fact 
we believe that even the most obtuse will not dispute the prop¬ 
osition that a lens in position C, Fig. 36H, must of necessity 
have the diameter shown (7j4 inches) in order to receive 
as great an amount of light as is received by the 4% inch 
lens opening in position F. 

The perpendicular dotted lines represent the faces of lenses 
at different distances from the center of the crater as shown, 
















MANAGERS AND PROJECTIONISTS 


163 


and the diameter each lens would have to be in order to have 
light collecting power equal to the 4% inch lens in position 
F is also given. It will be observed that at 3 inches a 5 inch 
diameter lens would be required, and at 3 l / 2 and 4 inches, a 
5% and 6J4 inch lens would be required. We believe this 
diagram will be rather startling to some projectionists who 
have paid no especial attention to the distance of their crater 
from the lens, and who have given no study to the practical 
operation of the law we have so often quoted in the Pro¬ 
jection Department of Moving Picture World, which is again 
quoted at the beginning of this subject. 

With the foregoing in view the importance of getting the 
light source as near the collector lens as possible is clearly 
seen, since, due to reasons which will be hereinafter ex¬ 
plained, the diameter of the condenser lens is limited. 

CAUTION. —In the foregoing connection let it be clearly 
understood, we do not mean that if the arc be retarded a 
given distance further away from a collecting lens of a given 
diameter the light loss would be as great as might be in¬ 
ferred from an examination of diagram, Fig. 36H. Fig. 36H 
is absolutely correct, but the fact remains that about 63 per 
cent, of the light is concentrated upon 50 per cent, of the 
area of the center of the collector lens, hence we could 
retard the arc a sufficient distance to equal a loss of 50 per 
cent, of the area of the collector lens and yet only lose about 
37 per cent, of the light. 

To enter into a detailed explanation of the reasons of this 
would not, we believe, be wise because the matter is largely 
one of geometry and would be very difficult for the mind of 
the average man to grasp. However, let it be clearly under¬ 
stood that the concentration of 63 per cent, of the light into 
50 per cent, of the area of the collector lens in no wise 
impairs the correctness of the proposition set forth in Fig. 
36H. It does, however, operate to modify the amount of loss 
when we deal with a collector lens of given diameter at 
different distances from the light source. 

The first task in the adjustment of the optical train of the 
projector is, therefore, to ascertain how near an electric arc 
may be located to the collector lens without causing the lens 
to break under the influence of rapid expansion and con¬ 
traction caused by excessive heat. It is this factor which 
forms the basis of the lens charts, and the arc is auto¬ 
matically placed the minimum distance it is possible to 
establish the crater of an electric arc of a given amperage 


164 


HANDBOOK OF PROJECTION FOR 


from a lens when lens charts are used. It is partly because 
of the fact that when Moving Picture World lens charts are 
applied this minimum distance is automatically established 
that we earnestly recommend all projectionists whose amper¬ 
age is within the limits of the charts to use them. It is 
hardly a practical thing for the projectionist to determine 
by experiment exactly what the minimum distance is, and 
then figure out the lens combination necessary to give the 
proper size spot at the proper distance. 

OPTICS OF THE CONDENSER.— The condenser may be 
composed of either two or three lenses, but the universal 
practice both in the United States of America and Canada is 
to use only two, though to some extent in England the three- 
lens combination is used, and in Germany we understand 
that it is used almost exclusively. In the two-lens com¬ 
bination the lens next the light source is known as the “col¬ 
lector” lens, and the front lens is known as the “converging” 
lens. Where there is a three-lens condenser the lens located 
between the collector and converging lenses is known as 
the “centre” l^ns. There are great possibilities for light loss 
inherent in the condenser itself. 

DISCOLORED LENSES. —When light passes through per¬ 
fectly clear, colorless glass of good quality, only a very 
small percentage of its energy is absorbed. In this we refer 
only to the actual passage of light through the glass—not the 
loss incident to reflection as the light enters and leaves the 
lens. Competent authorities place this absorption loss at 
about 1 per aent. per each inch of glass, for high grade 
glass. Other competent authorities place it at about .5 of 
1 per cent, per centimeter, which is a little higher than 1 
per cent, per inch. 

When a lens is discolored experiments have proven that 
the actual absorption loss is not greatly increased. The fol¬ 
lowing figures are from measurements of discolored con¬ 
denser lenses and give some idea of what it amounts to: 

Kind of Discoloration Focal Length Percentage of light passed by 

Plano-Convex discolored lens as compared to 

Lens. light strength without any lens 

at all. 


Slight green 7 7/16 inch 

Pressed lens, yellow 71/16 “ 

Pressed lens, yellow 71/16 “ 

Dark green 6 11/16 “ 


88.8 per cent. 

89.2 “ 

88.8 “ 

87.2 “ 


Many other lenses were measured, but the results were all 
within a range of 89.2 high and 87.2 low. When it is con- 


MANAGERS AND PROJECTIONISTS 


165 


sidered that both reflection and ordinary absorption losses 
are recorded together with the color loss, it is seen that the 
color loss must be slight. 

It does not, however, at all follow that color in condenser 
lenses is not harmful. As a matter of fact it is harmful, 
because it changes and injures the color value of the light. 
True, the color may not actually absorb very much of the 
total light, but it does alter and lower its value for pro¬ 
jection purposes. For instance: The light from a condenser 
having a greenish cast is “muddy.” It is not clear and bril¬ 
liant, hence its value for projection purposes is lowered. 

It seems, however, that the pink color sometimes found in 
condenser lenses which have been used for a time may pos¬ 
sibly not be detrimental, but in fact beneficial. Now that we 
know color in the lens does not, as formerly presumed, 
necessarily mean excessive loss of light, it might be well to 
experiment with color to some extent, but if this is done 
the colors must be confined strictly to those tending to 
mellow the light, without seriously affecting its brilliancy. 
A slight pink tinge might be beneficial. At least this dis¬ 
covery opens up a field for investigation, though the fact 
that tinted film must be projected cannot be overlooked. 

AVOID COLOR.—But in any event, except for experi¬ 
mental purposes, until this matter be finally settled, the pro¬ 
jectionist should avoid all color. In purchasing lenses, any 
lens which shows the slightest trace of color, when looked 
through EDGEWISE, should be promptly rejected. 

In examining lenses for discoloration, however, be very 
certain that any apparent color is actually in the lens itself, 
and not due to surroundings. 

THROW THEM AWAY.— The projectionist should always 
look through his condenser lenses edgewise when cleaning 
them, and should any discoloration appear he should promptly 
discard the lens, explaining to the manager that the lens 
may in a very short time use up the price of a new lens in 
light brilliancy. This should invariably apply to green, and 
should be the rule for all colors, until such time as it may 
become an established fact that certain colors are desirable— 
if it ever is. 

PITTED LENSES— When using certain types of carbon 
there is a decided tendency to pitting of the collector lens. 
The question is often asked, does this pitting cause light loss? 
The answer is, to a certain extent, yes, but this loss is not 
as large as might be supposed. The pit consists of a spot 


166 


HANDBOOK OF PROJECTION FOR 


from which the polish of the lens has been burned by impact 
with incandescent bits of carbon or metal. The light rays 
striking the lens at this spot are diffused, and a greater per¬ 
centage of the light is reflected from such a spot than would 
be reflected if the polish were perfect. The diffused light, 
of course, passes through the lens and reaches the spot. Just 
exactly what loss there may be, other than that due to re¬ 
flection at the point of incidence, we are unable to say. We 
believe, however, that practically all the light passed by the 
pitted spot will reach the spot. It seems to us, however, that 
a pitted condenser must necessarily place a considerable ad¬ 
ditional strain on the optical properties of the rest of the 
system, which may result in loss of definition of the picture. 
Of this we are not entirely certain, but believe it to be true 
because of the fact that the pitted point will diffuse instead 
of refracting the rays which strike it. 

In any event, bearing in mind the fact that condenser 
lenses are a comparatively cheap commodity, and that any 
injury to the screen result will inevitably result in the sale 
of less seats, we would suggest that it is poor policy to use 
a badly pitted condenser lens. Better throw it away and 
install a lens that you know is all right. 

THICKNESS OF LENSES.— Projectionists will have ob¬ 
served that some condenser lenses have a very thick edge, 
and some a rather thin edge. The condenser lens should by 
all means be standardized in these dimensions. It is neces¬ 
sary that a condenser lens edge have at least 1 / 16th of an 
inch thickness, because if it were brought right down to a 
sharp edge the tendency to breakage would be greatly 
increased. 1 / 16th of an inch is, however, ample, insofar as 
prevention of breakage be concerned, and since additional 
thickness of a glass tends in any event to absorb light 
energy to some extent, especially if the glass be of poor 
quality, it therefore follows that condenser lenses should 
have a standard edge thickness of 1 /16th of an inch, thus 
minimizing the thickness of the lens. 

In Fig. 37 we see at A a lens having unnecessary edge 
thickness, and at B a lens having the correct thickness of 
edge. Condenser lenses should have standard ¥/ 2 inch 
diameter—not pretty nearly but exactly. Another point is 
that the more nearly lens edge thickness and diameter be 
exactly standardized the more nearly will projector manu¬ 
facturers be able to make condenser mounts which will 
properly receive and support the lens. 


MANAGERS AND PROJECTIONISTS 


167 


CONDENSER LENS SURFACE.— It is highly essential to 
even screen illumination and efficiency of service that con¬ 
denser lenses be ground to a perfectly true surface and well 
polished. 

In Fig. 38 we see a condenser over which is placed a metal 
plate in which are drilled two small holes near the edge of 
the lens. The resultant rays pass through the aperture, as 
will be seen, and are by the condenser directed straight 
through to spots on the screen. 

In Fig. 39 we see the same thing exactly, except that the 

projection lens 
has been 
placed in po¬ 
sition. These 
are actual 
photo graphs 
taken of light 
rays, exactly 
as shown. A 
study of them 
will, we be¬ 
lie v e, con¬ 
vince even the 
most skeptical 
that the con¬ 
denser actual¬ 
ly directs* or 
projects the 
ray forward in 
a straight line 
toward the 
spot, aperture 
and projection 
lens. Now if 
the converg¬ 
ing lens has 
not a perfect¬ 
ly true sur¬ 
face it natur- 
a 11 y follows 
that instead 
of the rays be¬ 
ing all direct- 
e d forward 



Figure 37. 









168 


HANDBOOK OF PROJECTION FOR 


symmetrically to their proper place, the refraction will be 
uneven, the resultant illumination of the film will also be un¬ 
even, and since the projection lens receives the image of the 
film exactly as it is illuminated by the condenser, it follows 
that the screen itself will be unevenly illuminated. 

We learn from this the importance of having a condenser 
with a ground surface of perfectly true curvature. 

The condenser lens which has poor polish will be a source 
of continual loss, because the poorly polished surface will 



Figure 38. 

reflect a greater percentage of the light than will one with 
high polish. Optic Projection, page 602, paragraph 841, says: 

The polished surface of a lens reflects some light, about 
4 per cent, or 5 per cent, at each surface between glass and 
air; 8 per cent, to 10 per cent, for each lens or plate of glass. 
If the surfaces of the glass be not perfectly clean or per¬ 
fectly polished the light losses may amount to much more, 
sometimes 15 per cent, at each surface. 

We thus see the great importance of having not only 
perfectly clean lenses but lenses with highly polished sur¬ 
faces. 

TYPES OF CONDENSER.— In the United States and 
Canada only two types of condensers are in use, viz.: The 
plano-convex and the meniscus bi-convex two-lens com¬ 
bination, both having a standard diameter of 4 l / 2 inches, and 
a free opening of about 4 % inches when unobstructed by a 
slide carrier. 

The plano-convex combination consists of two plano-con¬ 
vex lenses, such as are shown in Fig. 37, set with their 
convex surfaces toward each other. The only effect of 
placing these lenses with their flat sides together would be 
a greater loss in reflection from the surface of the collector 
lens, and decidedly more spherical aberration. The meniscus 
bi-convex consists of a meniscus collector lens, which same is 
a lens having a convex surface on one side—the side toward 
the screen—with a slightly concave surface on the other, and 




MANAGERS AND PROJECTIONISTS 


169 


a bi-convex lens, which is a lens having two 
convex surfaces. 

The ordinary custom is to use the plano¬ 
convex combination, except under condi¬ 
tions where it is desirable to have the 
maximum possible distance between the 
condenser and film with the least possible 
distance of the arc from the lens, in which 
case the meniscus bi-convex combination is 
substituted. The advantage of the meniscus 
bi-convex combination is that a meniscus 
lens has a shorter working distance than 
either the plano-convex or the bi-convex of 
equal focal length, hence it may be used to 
advantage in reducing the working distance 
(distance from lens to light source) without 
enlarging the spot, or to reduce the size of 
the spot without increasing the working 
distance. 

Some projectionists claim other advant¬ 
ages for the meniscus bi-convex, but up to 
this time these advantages have not been 
demonstrated to the satisfaction of the 
author of this work, though it is possible 
there is some reduction of chromatic and 
spherical aberration by reason of the fact 
that the negative curvature in the meniscus 
to some extent neutralizes the positive 
curve. The negative curve is so slight, how¬ 
ever, that we believe its effect will be more 
than counterbalanced by the additional 
aberration set up by the bi-convex lens 

SMALL DIAMETER CONDENSERS.— 

In some countries it is the general custom 
to use a three-combination condenser of 
considerably smaller diameter than our 
standard. With this practice we are not 
well acquainted, but it undoubtedly possess¬ 
es some points of excellence, particularly 
under certain conditions. In cases where 
heavy amperage is used, with the conse¬ 
quent large crater and short distance between the condenser 
and film, and the resultant wide divergence of the beam 
beyond the aperture, there will be no advantage in the 4 



Figure 39. 



170 


HANDBOOK OF PROJECTION FOR 


inch condenser if the divergence of the beam.be such that the 
ray cannot be picked up in its entirety by the projection lens. 
In cases of this kind there certainly would be advantage in a 
smaller diameter condenser, if for no other reason than that 
it would give a thinner lens, with consequent slightly less 
light absorption, and the possible shorter working distance 
between the crater and the collector lens. We believe pro¬ 
jector manufacturers would do well to examine into the merits 
of the small diameter three-lens condenser combination more 
closely than has, so far as we have knowledge, been done in 
this country up to this date. 

One other serious disadvantage of the larger diameter 
condenser is that its outer zones produce considerable 
chromatic aberration, and this impure light is carried down 
into the centre of the beam at the spot by spherical aber¬ 
ration, which tends to lessen the brilliancy of the whole spot. 

SPACING OF CONDENSER LENSES.— No matter what 
your condenser combination may be, the lenses should always 
be spaced so that the nearest surfaces are within not more 



Figure 40. 

than 1 / 16th of an inch of each other. Optically the best 
possible position would be with the surfaces actually in con¬ 
tact, but this would communicate heat from the collector 
lens to the converging lens by mechanical means, which 
would be highly objectionable. The lenses should be just 
sufficiently separated to avoid this. 

Lens tables are calculated on the equivalent focus of con-' 
denser lenses set with their nearest point of contact sepa¬ 
rated not to exceed 1 / 16th of an inch, and spacing the lenses 





MANAGERS AND PROJECTIONISTS 


171 


further apart has the effect of altering the equivalent focus 
of the combination, besides setting up additional and un-* 
necessary loss as follows: 

LIGHT LOSS BETWEEN THE CONDENSERS.— The col¬ 
lector lens, the one next the light source, does not send for¬ 
ward a parallel beam when the arc is in correct position for 
projection. 

In Fig. 40, we see the rays sent forward by a 6.5 inch focal 
length collector lens, when the arc is in projection position. 

Now stop and consider for a moment. Examining Fig. 40, 
it will readily be seen that loss of light will occur between 
the lenses of the condenser, and the farther away the con¬ 
verging lens is from the collector lens—the greater the 
separation of the two lenses—the greater the loss will be 
because of the fact that the outer margin of the beam sent 
forward by the collector lens falls outside the converging 
lens. 

The projectionist has only to observe the ring of light 
surrounding the converging lens of his own projector to 
understand the truth of this. 

CONDENSER MOUNTS. —Most of the late types of pro¬ 
fessional projectors have very good condenser mounts. A 
condenser mount should have the following points of excel¬ 
lence: (a) accessibility, in a way that will allow the pro¬ 
jectionist to readily get at the lenses and to remove a hot 
lens with a minimum effort and in a minimum space of time; 
(b) the lens should be in firm contact with the metal of the 
holder around its entire edge, and the lens holder should be 
so calculated that it will act as a heat equalizer, causing the 
thin edge of the lens to heat up and cool down as nearly 
as possible at the same speed as does the thick centre of 
the lens; (c) the lens holders should be so made that the 
distance between them may be altered quickly and con¬ 
veniently from the outside of the casing, in order to properly 
adjust the distance between lenses of varying thickness, or 
to adjust them for other reasons ; (d) the condenser holder 
should be strongly and substantially made, and when in 
projection position should be locked firmly in place; (e) 
modern methods favor the placing of the condenser inside the 
lamp house, which is, in our opinion, the better practice, 
since it subjects the whole condenser to the even, though 
high, temperature of the lamp house interior. 

CONDENSER BREAKAGE.— Often this is a difficult thing 
to deal with. Cases of excessive breakage have come under 


172 


HANDBOOK OF PROJECTION FOR 


the observation of the author for which there was, apparently, 
no reason. As a general proposition, however, always pro¬ 
vided the condenser lenses be properly mounted (see con¬ 
denser mounts, page 365) excessive breakage will be found 
to be due to one of three things, viz.: (a) an improperly 
selected or improperly adjusted optical system which places 
the arc too near the collector lens; (b) excessive heat in 
the lamp house due to improper ventilation thereof (see 
lamp house ventilation, page 362); (c) excessive flaming of 

the carbons. 

WHAT THE CONDENSER DOES.— The condensing lens 
acts, in a way, the same as does a photographic lens, form¬ 
ing an image of the floor of the carbon crater, or the Mazda 
filament, though the whole of the first named is not in focus 
at one plane, because it sets at an angle to the plane of the 
lens. The floor of the carbon crater is not, as has been 
demonstrated by experiment, of even luminosity. This is 
probably due to variation in the carbon itself, and to the 
further fact that the core in the center of the carbon offers 
a different degree of luminosity to the area of the crater 
surrounding it. If, therefore, the condenser project for¬ 
ward to the film plane a sharply focused photograph of the 
floor of the crater it follows that the film will be unevenly 
illuminated, and since the film is one of the conjugate foci 
points of the objective lens, also follows that the screen itself 
will be unevenly illuminated. 

It therefore is important that the actual image of the 
crater be more or less “broken up,” which is in good measure 
accomplished by reason of the fact that the floor of the 
crater does not set parallel with the plane of the lens, hence 
is not and cannot be focused in its entirety at the film plane, 
and to the further fact that the condenser contains con¬ 
siderable spherical aberration, which has the effect of 
helping to break up the image, and thus produce an evenness 
of illumination at the film plane. 

LOCATION OF CRATER IMAGE.— In the stereopticon the 
image of the crater is focused within the projection lens itself. 
Theoretically this would be the proper place to focus the 
crater in motion picture projection, but in practice it is found 
that where the light source is a carbon crater this is not 
practical. It is difficult, if not impossible, to get evenness 
of screen illumination with the main point of focus of the 
crater too near the aperture. The practice which generally 
gives good results is to focus the center of the crater slightly 





MANAGERS AND PROJECTIONISTS 173 


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174 


HANDBOOK OF PROJECTION FOR 


on one side or the other of the film plane, but if an attempt is 
made to focus the crater image too far on the projection 
lens side of the film plane the ghost zone of the condenser 
beam (see page 177) will be encountered. 

This point has caused a great deal of discussion and dis¬ 
sension among those striving to solve the problem of the 
optics of the projector. Theoretical opticians have insisted 
on basing their calculations for motion picture optics on a 
crater focused either within the projection lens or else far 
on the screen side of the film, and this has been one of their 
stumbling blocks, since it just simply refuses to work out 
in practice. 

SHAPE OF SPOT. —The projectionist will do well to study 
the shape of his spot, since in it he finds a direct indication 
of the condition of his crater. He should remember that the 
spot is an out-of-focus image of the floor of the crater, and 
that the more nearly round the spot is the more nearly his 
crater condition will be found to be perfect, insofar as has to 
do with light projection. A perfectly round sharply defined 
spot is a very good indication that the crater is good, and 
that its position with regard to its angle to the lens is good. 
See high intensity arc, page 773. 

SIZE OF SPOT.— When we consider the size of the spot 
at the aperture of the projector we find it a subject full of 
complications. About the smallest spot that can be carried 
with an assurance of maintaining a clear screen is 1^4 
inches in diameter. The modern projectionist, however, as a 
general proposition prefers the 1.75 inch-diameter spot, since 
with the smaller one there is always the chance for the 
appearance of discoloration of the light on the screen, a thing 
which must at any cost be avoided. 

Fig. 41 is the diagrammatic representation of the possi¬ 
bilities for loss of light through unnecessary enlargement of 
the spot. With a spot 1.5 inches in diameter, only 43 per cent, 
of its area covers the aperture, the rest being intercepted by 
the cooling plate. We thus see that with a spot of minimum 
practical diameter, 57 per cent, of its area is intercepted by 
the cooling plate. If we increase the size of the spot to 2.75 
inches diameter, then the aperture will only cover 13 per cent, 
of the area of the spot, 87 per cent, of which will be inter¬ 
cepted by the cooling plate. 

The obvious lesson of this is that an unnecessarily large 
spot is an enormous waster of light, hence of electric energy. 

In this connection let us consider that 


MANAGERS AND PROJECTIONISTS 


175 


The main point in deciding upon the focal length of the 
condenser, is to secure a focal length which will establish the 
crater produced by the amperage to be used at the minimum 
practical distance from the collector lens, at the same time 
giving the smallest practical diameter of spot and a maximum 
distance from the center of the condenser to the aperture. 
(See page 162.) 

The latter, however, is only of importance in cases where, 
due to the large diameter crater produced by high amperage, 
;t is difficult to secure sufficient distance between the center 
of the condenser and the aperture to confine the divergence 
of the beam beyond the aperture within limits which will 
enable the objective to pick up the entire beam, and at the 
same time keep the spot at the minimum practical working 
diameter. 

In considering the relation of the focal length of the con¬ 
denser to the size of the spot, to the distance from the 
center of the condenser to the spot, to the size of the crater, 
and to the distance of the crater from the center of the con¬ 
denser, let is be clearly understood that while the office of 
the condenser is to intercept as much as possible of the light 
emerging from the crater, and to concentrate it on the 
aperture, it after all, in so doing acts precisely the same as 
would a photographic lens. With a condenser of given focal 
length, and a crater of given diameter, the diameter of the 
spot will be as many times the diameter of the crater as the 
distance from the apex of the curved surface of the collector 
lens to the floor of the crater is contained times into the 
distance from the apex of the curved surface of the con¬ 
verging (front) lens to the aperture, when the curved sur¬ 
faces of the lenses are not to exceed l/16th of an inch apart. 
For instance: If the distance from the apex of the curved 
surface of the collector lens to the aperture is 16 inches, the 
distance from the apex of the curved surface of the col¬ 
lector lens from the floor of the crater 4 inches, and the 
crater is .5 of an inch in horizontal diameter, then the re¬ 
sultant spot will be 16 -r- 4 = 4, and 4 X y 2 inch = 2 inches 
in diameter. This applies equally for both plano-convex and 
meniscus bi-convex lenses, except that when figuring the 
meniscus bi-convex, instead of figuring from the curved sur¬ 
face to the floor of the crater we figure the distance from a 
point of an inch in front of the convex face of the meniscus 
lens, and the other distance from the center of the bi-convex 
to the aperture. 


176 


HANDBOOK OF PROJECTION FOR 


With the foregoing in mind it readily will be seen that the 
necessary enlargement of the crater image at the spot will 
depend on the number of amperes we are using, since the 
diameter of the crater increases in proportion to the number 
of amperes used. (See Page 393.) The distance from cra¬ 
ter to apex of curved surface of collector lens, and from the 
apex of curved surface of converging lens to film, are known 
respectively as “distance X” and “distance Y.” The points 
from which they start are shown in Fig. 42. 

The average pro¬ 
jectionist who reduces 
his spot diameter by 
pulling his lamp back 
a greater distance 
from the face of the 
collector lens is more 
than likely to discred¬ 
it the foregoing, be¬ 
cause, while he has 
decreased his spot 
diameter, he has 
either not increased 
the screen illumina¬ 
tion at all, or to no 
appreciable extent. 

The fact is, he has 
not acted intelligent¬ 
ly. He should have installed a shorter focal length condenser 
in order to maintain his arc-to-lens distance at minimum, at 
the same time setting up a condition which would cause a 
heavier convergence of the beam on the other side of the lens. 

Of course we realize that intelligent work in this direction 
is hampered by difficulty in securing lenses of necessary 
focal lengths, but much may be accomplished, nevertheless, 
and the whole matter forms an interesting and profitable 
field for experiment and study on the part of projectionists 
and engineers. 

The problem is to keep distance X the minimum possible, 
without setting up excessive lens breakage, at the same time 
maintaining a maximum distance and standard diameter spot. 

In this connection remember that: 

The spot diameter will always be as many times the diame¬ 
ter of the crater as distance X is contained into distance Y. 



M£N/SC</5 8/-CQMVCX. 


Figure 42. 









MANAGERS AND PROJECTIONISTS 


177 


SLIDE CARRIER WASTE.— The loss of light caused by 
fixing a slide carrier permanently in place in front of the con¬ 
denser is illustrated in Fig. 42A. 

Lack of understanding and appreciation of such things 
causes what is literally a tremendous amount of waste of 
light, which means electric energy, when we come to consider 
motion picture theatres as a whole. Each theatre may waste 
but comparatively little, but there are many thousands of 
theatres. 

CRATER IMAGE UPSIDE DOWN.— Due to the fact that 
the condenser reverses the image of the crater in projecting 

it, the image 
of the crater 
is upside down 
at the spot. In 
some cases 
where the 
bottom of the 
crater is in 
fairly good 
focus at the 
cooling plate 
it is possible 
to discern the 
image of the 
lower carbon 
tip at the top 
of the cooling 
plate. It may 
often be clear¬ 
ly seen when 
feeding the 
carbons while 
the arc is 
burning. 

GHOST 
ZONE. — The 
con dens e r 

beam carries a well defined ghost zone. This is due to chro¬ 
matic aberration, which is always present in uncorrected 
lenses such as those used for condensing. 

In Fig. 43 a crater is constructed by cutting an aperture 
in a piece of cardboard and placing over it a bit of ground 
glass, behind which we establish a 100 C. P. incandescent 


AREA OF A'/z" CONDENSER LENS 15.9 S^.IN. 
AREA OF BLACK CIRCLE, W WIDE, 2.5+ SQ. IN. 
OR 16% OF THE TOTAL AREA OF THE LENS. 


DRAWN TO SCALE 



Figure 42A. 






178 


HANDBOOK OF PROJECTION FOR 


lamp. The crater and the screen are placed at conjugate 
foci points of the plano-convex condenser, as shown. The 
screen corresponds to the aperture of a projector. We cover 

the front surface of 
the collector lens 
with a piece of 
cardboard in which 
is a pin hole located 
as shown. 

The results as ob¬ 
served upon the 
screen are: The 
crater is focused in 
full definition, but is 
colored with the 
shades of the spectrum in the manner shown. It has been 
demonstrated by the Kinemacolor process that all the colors 
of the spectrum may be reduced to approximately two shades, 
viz.: A reddish-orange and a bluish-green, which, for the 
sake of clearness, we will call orange-green. 



In Fig. 44 the same conditions are shown as those described 
in connection with Fig. 43, except that the colors of the spec¬ 
trum have been reduced to the two primary shades, viz.: 
Orange and green. You will note that under this condition at 
the screen (or aperture) the colored rays have combined and 
formed white light. 

Now if the process shown in Fig. 44 be continued, and a 
very large number of rays be drawn, using orange and green 
ink, the result will be as illustrated in Fig. 45, which is 
merely Fig. 44 elongated to more nearly approach actual 
working conditions. 

In Fig. 45 it is ob¬ 
served that the beam 
is enclosed by an 
orange envelope, 
which is thickest 
toward the central 
part of the beam 
and comes to a 
point, or is not 
present at the aper¬ 
ture and the condenser. The beam has a core in its center, 
which same is composed of the violet, the blue aijd the green 
shades of the spectrum. The white part of the beam is caused 















MANAGERS AND PROJECTIONISTS 


179 


by the mixture of the two other primary shades, but the mix¬ 
ture is not perfect at all positions. At AA Fig. 45 the white 
light is most pure, but as it approaches position BB the colors 
at the faulty end of the spectrum begin to predominate, so 
that at section BB the white zone has changed to a dirty 
purple. Considering this condition we may readily understand 
why a ghost appears when the condenser is brought far 
enough toward the aperture. 

When the aperture is properly located, all the colors oi 
the beam finally combine at that point to form pure white 
light, and all light beyond the aperture is white. 

It must, however, be remembered that the results shown 
in Fig. 45 can only be approximately true, since all the colors 
of the spectrum, which are infinite in number, have, for the 
purpose of the experiment, been reduced to two shades. 



Figure 45. 


Even if only seven of the primary colors have been used in 
the drawing, the straight lines in Fig. 45 would show as 
curves, and more closely resemble the true shape of the 
actual beam. 

The projectionist is not able to see these various zones 
with the naked eye. The fact remains, however, that while 
invisible to the eye they are there, and it is their presence 
which causes the blue spot to appear in the center of the 
screen when the aperture is brought too near the condenser, 
or the crater is advanced too close to the collector lens, 
which latter has the effect of advancing the ghost zone 
nearer to the aperture. 

PURE LIGHT. —In this connection one of the important 
functions of having the crater as nearly as possible in focus 
at the aperture is to purify the light and avoid color effects. 

ADJUSTING THE PROJECTOR OPTICAL TRAIN.— Be¬ 
fore attempting the adjustment of the optical train it will 
be well to carefully study and consider all those various 
things which have already been set forth under the general 









180 


HANDBOOK OF PROJECTION FOR 

heading “Lenses,” beginning at page 125. We will provide 
you with the necessary charts and diagrams, by the applica¬ 
tion of which you will be able to so adjust your projector 
optical system that maximum results will be had, both in 
brilliancy and evenness of screen illumination, and, what is 
almost equally important, they will be had at maximum 
efficiency. 

It must be remembered, however, that where local condi¬ 
tions vary so widely, even the most carefully calculated and 
prepared formula is likely to in some measure fail of its 
highest purpose unless it be applied with intelligence and 
understanding. It is for this reason we urge projectionists 
to study and come to an understanding of the underlying 
principles which govern in the selection and adjustment of 
the projector optical system. 

It is a deplorable fact that the lack of such understanding 
on the part of projectionists, coupled with the failure of 
condenser lens manufacturers to provide proper lenses and 
the failure of theatre managers and exhibitors to purchase 
optical equipment of the right design and quality, has, ever 
since the very inception of motion picture projection, not 
only caused a literally huge waste in light, which means a 
waste in electric energy, but has also made it impossible to 
exactly duplicate the illumination of all points of the film 
photograph upon the screen, without which it is impossible 
to secure the same apparent depth in the picture which the 
natural scene presented to the “eye” of the high grade 
camera lens, and which was by that lens impressed faith¬ 
fully upon the film. 

It has often been remarked that the same photoplay has 
an apparently increased stereoscopic effect, or perhaps we 
might better say a greater “depth” in one theatre than in 
another, and this has been placed to the credit of the screen, 
whereas the real credit was not due to the screen at all, but 
to the correct selection of the various elements of the optical 
system and their correct adjustment with relation to each 
other, so that the film image was evenly illuminated and the 
evenness of illumination was faithfully transmitted to the 
screen. 

One of the big outstanding facts in projection is that even¬ 
ness of illumination is absolutely essential to perfect results 
on the screen, and evenness of illumination at the screen is 
impossible unless we first secure evenness of illumination of 
the film photograph at the aperture, and then project the 


MANAGERS AND PROJECTIONISTS 181 

even illumination of the picture at the aperture to the screen 
without change. 

It is a comparatively simple problem to secure at least a 
high degree of evenness of illumination at the aperture, but 
a study of the subject will convince even the most skeptical 
that unless the projection lens receive an equal amount of 
light from every point of the area of the aperture there can¬ 
not possibly be evenness of illumination at the screen. 



Figure 46. 

If the student will carefully examine Fig. 46 and apply its 
meaning he will, for one thing, immediately know that a pro¬ 
jection lens which has not sufficient diameter to receive the 
entire beam from the aperture, cannot possibly distribute 
evenness of illumination of the film photograph to the 
screen. 

Fig. 46 is a photograph, in which X is a standard projector 
aperture, mounted on an optical bench, over which has been 
placed a plate of metal in which two minute holes were 
drilled. This aperture is illuminated by a standard spot 
from a regular projector plano-convex combination conden¬ 
ser, placed with its center 18 inches from the aperture. 1 is 
the rear combination of the projection lens, and 2 the front 
combination, space Y having been sawed out of the lens 
barrel so that we were able to look right into the lens and 
watch the action of the rays. Smoke was blown into the 
light beam, thus making it visible and enabling us to pho¬ 
tograph the results. Absolutely no change has been made 
in the photograph, except that we have drawn in the black 
dividing lines between the two light cones which, while quite 
visible in the photograph itself, would not show in the 
printed reduction. 

Considering Fig. 46 you will see that a cone of rays goes 
forward, diverging fan-shaped, toward the projection lens. 
That this is true you ought to know because, since every 
pin point of the film photograph must be refocused on the 



182 


HANDBOOK OF PROJECTION FOR 


screen in its appropriate place, it follows that the illumina¬ 
tion it receives must go forward to the projection lens as a 
separate unit, and by the projection lens must be sent for¬ 
ward to its appropriate spot on the screen. 

Consequently we must treat every pin point of the film 
photograph as an entirely separate proposition from every 
other pin point when we consider the item of illumination, 
and the projection of that illumination to the screen. 

If every portion of the film photograph is evenly and 
equally illuminated it follows that the light from each pin 
point of the film goes forward toward the projection lens 
as a cone-shaped bundle of rays, the base of which is at the 


ft 



projection lens. Since the amount of divergence of the rays 
is in exact proportion to the diameter of the condenser and 
its distance from the aperture, the cone starting at the center 
of the film picture is always likely to enter the projection 
lens in its entirety, which means that the full value of the 
illumination passing through that point will be projected for¬ 
ward to its appointed place on the screen, giving the center of 
the picture on the screen what we may call 100 per cent, 
illumination, appearing to the audience practically the same 
as it appeared to the eye of the camera. 

On the other hand, again considering Fig. 46, suppose one 
of these cones to have its point at the extreme corner of the 
projector aperture. This cone will also diverge equally with 
the one in the center of the picture, and if the projection lens 
has insufficient diameter to receive its entire base, it is 









MANAGERS AND PROJECTIONISTS 


183 


apparent that a portion of this bundle of rays will fall outside 
the projection lens, hence will not be projected to the screen.. 
This, of course, means that that particular point of the film 
photograph will be deficient in illumination, and therefore 
will not have the apparent depth presented by the center of 
the picture. 

That this unevenness of illumination may not be in any 
degree apparent to the eye when the blank screen is viewed 
proves nothing, because the eye is unable to detect uneven¬ 
ness of illumination under those conditions unless it be very- 
great indeed, or unless the weak points be also discolored. 
But it can and does detect the difference in apparent depth 
of the picture, though it does not recognize it as such. In 
fact, it does not recognize it at all, and could not possibly 
recognize it except in case two projections of the picture be 
placed side by side, one evenly illuminated and the other 
not evenly illuminated. The eye would then see that the 
evenly illuminated picture was much more pleasing than the 
one which was unevenly illuminated. 

In Fig. 47 we have diagrammatic representation of what 
we have been talking about with relation to Fig. 46. A is a 
standard aperture in which dots X and Y represent respec¬ 
tively two pin points in the film photograph, one in the cen¬ 
ter and one in the upper left hand corner. B is a line 
representing a side view of the same aperture. C is the back 
factor of a 1 j4-inch-diameter projection lens, at 4-inch work¬ 
ing distance. Cones D, E, F and G are laid out exactly as 
they would be with a standard diameter condenser converg¬ 
ing lens located 18 inches from aperture B. Dotted line 
H—H represents the diameter of projection lens C. In other 
words, lines H—H represent the diameter of lens C at any 
point within their length, and we may readily see that in 
order to take in the entire cone D—E, the lens would neces¬ 
sarily have to be moved towards the aperture to point J. 
Dotted lines I—I represent the diameter projection lens C 
would have to have in order to accommodate cone D—E in 
its entirety. 

It seems hardly necessary to point out the very obvious 
fact that under this condition the center of the screen image 
must and will, in the very nature of things, be better 
illuminated than will the outer margins. In other words, 
under such a condition it is utterly impossible to have an 
evenly illuminated picture on the screen. 


184 


HANDBOOK OF PROJECTION FOR 


BEAM DIVERGES BEYOND APERTURE.—That the 

beam does diverge beyond the aperture (between aperture 
and projection lens) is amply proven in Fig. 48, which is the 
photograph of a standard projector aperture illuminated by 
a condenser, exactly as in practical projection. By laying a 
straight edge along the upper line of the diverging ray it 
will be found to just touch the lower edge of the condenser, 
and if the straight edge be laid on the lower edge of the 
light ray it will just touch the upper edge of the condenser, 
proving that the divergence of the ray is in exact proportion 



Figure 48. 

to the diameter of the condenser and its distance from the 
aperture, the size of the projector aperture being always 
standard. 

In Fig. 49 we have the photographic representation of 
what happens when the projector lens has insufficient 
diameter to receive the entire light beam. This not only 
results in serious loss of light, but, as has already been ex¬ 
plained, causes unevenness of illumination on the screen 
and detracts seriously from the depth of the picture. 

PROJECTION LENS DIAMETER AND CONDENSER 
DISTANCE. —Fig. 50 is the diagrammatic representa¬ 
tion of the effect of distance of condenser from aperture on 
projection lens diameter. In this drawing we have a con¬ 
denser with the face of the converging lens located 16 inches 
from the aperture. The broken lines indicate the divergence 




MANAGERS AND PROJECTIONISTS 


185 


of the beam at the plane of the pro¬ 
jection lens, which is presumed to be 
5 inches from the aperture—a 5-inch 
working distance. We have another 
condenser lens, of equal diameter, lo¬ 
cated 21 inches from the aperture, the 
divergence of the beam from which 
is indicated by the solid lines. We 
thus see that the removal of the con¬ 
denser to a greater distance from the 
aperture has the effect of narrowing 
the divergence of the beam beyond 
the aperture, thus permitting the use 
of a projection lens of smaller diam¬ 
eter. But let it be clearly understood 
that as we increase the distance from 
condenser to aperture it will be neces¬ 
sary to install longer focal length 
condenser lenses in order to maintain 
the size of the spot (assuming, of 
course, that the crater was in the first 
instance, the minimum distance from 
the face of the collector lens for 
the amperage being used), and the 
installation of a longer focal length 
condenser means that the crater will 
be farther away from the plane of the 
collector lens. This automatically sets 
up light loss (see Fig 36H), in that 
it reduces the amount of light flux 
falling upon the surface of the collec¬ 
tor lens, but if the projection lens was 
of too small diameter to pick up the 
ray, the increased amount of light it 
will receive by reason of the narrow¬ 
ing of the divergence of the ray will 
more than compensate for the loss at 
the condenser. 

CAUTION. —This is one of the 
things which must be applied with 
understanding, and the more thor¬ 
oughly the projectionist understands 
all the various propositions involved the better result he will 
be able to attain, both in screen illumination and efficiency. 



Figure 49. 




186 


HANDBOOK OF PROJECTION FOR 



LIGHT LOSS THROUGH DIVER- 

GENCE. —The following charts are 
from actual photometer readings of 
the ray at points A, B and C, Fig. 51. 

The black circle in each of the 
charts represents a projection lens 
with 2 inch free diameter. 

Fig. 52 is a measurement of the 
light beam 3 inches from the aperture, 
on the projection lens side of course 
(position A, Fig. 51), with the con¬ 
denser located with the face of the 
converging lens 10 inches from the 
aperture. Fig. 52 is a measurement 
made under the same condition, but 
taken at position B, Fig. 51, and Fig. 
53 is the measurement at a distance 
of 7 inches from the aperture, position 
C, Fig. 51. The black circle shows the 
area of the beam a 2-inch free open¬ 
ing projection lens would cover. 

Figs. 54, 55 and 56 are measurements 
made at position A, B and C, Fig. 51, 
but with the face of the converging 
lens of the condenser 18 inches instead 
of 10 inches from the aperture. 

Examining these charts we find sev¬ 
eral surprises. Let us take Fig. 53 for 
example, first, however, being sure 
you understand exactly what is being 
done. Imagine yourself looking at the 
front, or projection lens side of the 
aperture of a projector from which 
the revolving shutter, front plate and 
projection lens have been removed. 
You are then looking toward the con¬ 
denser and into what we will, for lack 
of a better term, call the “end” of the 
light beam from the condenser after 
it has passed through the aperture. 
The beam will spread out fan-shaped 
(diverging), as shown photographi¬ 
cally in Fig. 48 and diagrammatically 
in Fig. 51, the divergence being in 













MANAGERS AND PROJECTIONISTS 


187 


proportion to the distance of condenser from the aperture. 
Pardon the repetition, but it is essential that you grasp this 
fact and understand it clearly. 

Looking thus into the end of the light beam, we occupy 



the position of the photometer which measured the intensity 
of every portion of the beam in half inch sections of its area. 
In their outline all the charts show the exact shape and 
exact size of the beam at the point of measurement, which in 
Fig. 53 is at 5 inches from the aperture when the face of the 
converging lens of the condenser is 10 inches from the aper¬ 
ture. Each circle is a “zone” one-half inch wide, and each 
division thereof represents, in the figures printed on it, a 
measurement of its light intensity. 

This understood let us proceed to analyze chart 53 and its 
accompanying tabulation. The center zone shows a light in¬ 
tensity of 26-foot candles, but it carries a total of only .2 
lumens, because it has only .0077 of a square foot area. Its 
candle power is high, but its area is small. It represents the 
light the area of a inch circle at the center of the lens 
would receive. It amounts to only 3.4 per cent, of the total 
light giving power of the entire beam. Next we examine 
zone 2, which by the tabulation, we see has only an average 
of about 22 candle power unit area, but carries a total of 1.4 
lumens, because it has .062 of a square foot of area. Its 
candle power per unit of area is weaker, but its area is so 
much greater than zone 1 that it is found to carry 24 per 
cent, of the total candle power of the light beam, or almost 
8 times as much as the more brilliant center of the beam. 
Zone 3 we find to have an average of only 14.2 foot candles, 











188 HANDBOOK OF PROJECTION FOR 

but it nevertheless carries 30 per cent, of the total light of 
the beam, because it has many times the area of either ot the 
other zones. 

IMPORTANT.—Zones 1, 2 and 3 carry all the light which 
can get through the projection lens under the conditions 
shown. The rest U wasted, and a glance at the tabulation 
shows that the waste is 21.5 plus 21, or 42.5 per cent, of the 
total light. 

Of course the condition as to condenser location is ab- 



Zone 

Area 


Lumr*s 

YMaf 

/ 

9077 

I't.l 

.1 3 


z 

061 

111 

-88 

jfj 

3 

.72 3 

//A 

JW 

Ho 

4 

J63 

8.4 


264 

Jr 

21S 

.*9 

(17 

1S.2U 

re/no 

’Rinf z 

toes 

V 

7,0 



7o/«/ 

<£83 



Figure 52. 


Reduced by 1.25 inches, size of actual ray 4£4x4". 


















MANAGERS AND PROJECTIONISTS 


189 



Exact Shape and Size of Ray Five Inches from Aperture, on 
Projection Lens Side, with Condenser 10 Inches 
from Aperture. 


.Zone 

Are as 

A Ye.fC- 

C omens 

%Tot*J 

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Figure 53. 


















190 


HANDBOOK OF PROJECTION FOR 


normal, since in arc light projection it seldom or never is 
found so close to the aperture. But Figs. 55, 56 and 57 show 
a very normal condition—in fact a condition very much better 
than the ordinary, because it would mean a 19-inch center- 



Exact Dimension and Shape of Light 
Ray Three Inches from Aperture, 
on Projection Lens Side, When 
Condenser Is 10 Inches from 
the Aperture. 


Zone 

AreastV. 


Lumens 

%Total 

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Figure 54. 


of-condenser-to-aperture condenser oosition. We have shown 
you how to read these charts. Their study will be highly 
enlightening as to the possibilities for waste through wrong 
ondenser position, to say nothing of the loss of depth in the 




















MANAGERS AND PROJECTIONISTS 


191 


picture caused by unevenness of illumination inevitable under 
such conditions. 

LENS CHART. —An excellent lens chart constructed by 
John Griffiths was purchased by the Moving Picture World 
and published in the projection department some time ago. 



Seven Inches from Aperture, with Con¬ 
denser 18 Inches from Aperture. 


Zone 

Jffect 

fyF.C. 

lumens 

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/ 

.eoTf 

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X 

. 663 / 

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3 

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rem* 

nm<t Zo 


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To la! 

L2£ 



Figure 55. 


Its range is from 25 amperes to 60 amperes A. C. or D. C. 
within which limits it has proven iteslf to be efficient and 
satisfactory. It has a place in the projection rooms of a 
large percentage of motion picture theatres throughout the 
English speaking world. The construction of this cnart 
marked a very great advance towards perfection in the ad- 



















192 


HANDBOOK OF PROJECTION FOR 


justment of the projector optical system. We commend it 
heartily to projectionists whose amperage lies within its 
range. 

It has been found impractical to reproduce this chart here¬ 
with in a size sufficiently large to be of practical use. How¬ 
ever, large reproductions, measuring 9JX by IS inches, suitable 
for placing on walls of projection rooms, can be secured at 
a nominal price from Moving Picture World. 

HOW TO USE THE CHART. —First ascertain, as nearly as 

possible, what 
amperage you 
are using at 
the arc. If you 
merely “guess” 
at it, and don’t 
happen to hit 
things right 
don’t blame 
the chart if it 
does not give 
perfect results. 

Be sure that 
the condenser 
lenses are at 
least approxi¬ 
mately what 
they are sup¬ 
posed to be in 
the matter of 
focal length 
and that they 
are placed in 
the mount 
with their 

curved surfaces separated by not more than 1/16 of an inch. 

Let us assume an amperage of 50, D. C., and a projection 
lens working distance of 5 inches. 

The center of the chart is divided by a vertical column 
marked at the top “Distance to Aperture.” The right hand 
side of the chart is for plano-convex and the left hand side 
for meniscus bi-convex condensers. Looking on the right 
hand side we find that for 50 amperes D. C. we should have 
a 6and a 7}4 inch converging plano-convex lens, and that 
the line under 50 D. C. is just a little above the line “17 


" \_ 

\v< /v 

6.9 / \//,8 / v 6.i 
" -// 2 .? > r'" 

[70 I-( 17.9 )— 

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N 


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t. 7 r 



Figure 56. 
















MANAGERS AND PROJECTIONISTS 193 

inches” in distance from the aperture. We shall therefore 
require a collector lens and a 7}4 converging lens, spaced 
not to exceed 1/16 of an inch apart, with the center of the 
condenser just a little less than 17 inches from the aperture. 
With this combination, since our projection lens is at a 5 inch 
working distance it must have a 2.2 inch free diameter in 
order to accommodate the entire beam. 



Exact Size and Shape of Ray Three 
Inches from Aperture When Con¬ 
denser Is 18 Inches from Aperture. 


2on e 

Area 


Lumens 

% /okjJ 

1 / 


ay 3 

J9 

to & 

2 


/3 f 

,S6 

.X 

3 



■7° 

*fo,o 



Total 

f.ir 

/QO. 


Figure 57. 


If we find our projection lens has less than this free 
diameter, then there would be some gain in using a meniscus 
bi-convex set, because, looking under 50 amperes in the 
meniscus bi-convex side we find that the 6j4 meniscus and 
8 x / 2 bi-convex combination required for 50 amperes gives us 
a 2-inch greater distance between the center of the condenser 
and the aperture, so that a 2.1 projection lens working open- 















194 HANDBOOK OF PROJECTION FOR 

ing will accommodate the ray. Not very much gain, to be sure, 
but some. 

Aside from this gain the meniscus bi-convex does not pre¬ 
sent much, if any, advantage over the plano-convex, and we 
believe that the plano-convex and a reduction of condenser 
diameter would produce better general results. (See page 
203.) 

UNIVERSAL METHOD FOR ASCERTAINING CON¬ 
DENSER FOCAL LENGTH AND APERTURE DISTANCE 
WITH RELATION TO OBJECTIVE DIAMETER.— In Fig. 

58 we present a very valuable diagram by the careful, in¬ 
telligent application of which the projectionist using high 
amperage will be enabled to get both the correct condenser 
distance for his objective and the correct focal length con¬ 
denser to maintain the proper size spot at that distance. 
This diagram must, however, be used with caution, because 
there may be. a tendency to apply it in cases where the in¬ 
stallation of a projection lens of larger diameter would serve 
better. In other words, it would be bad practice to use this 
diagram for the purpose of accommodating a projection lens 
of too small diameter for the work, since if this be done, 
although there might be some gain as against the former 
condition, still the ultimate result will not be what it should 
be, and would be if a projection lens of proper diameter were 
used. The method of applying the diagram is as follows: 
First measure both the exact working distance of your 
projection lens and the exact free diameter of its aperture. 
Next examine Table No. 8 and in the left hand column find 
the number corresponding to, or most nearly corresponding 
to, the free diameter of your projection lens. Now run your 
finger out along the horizontal row of figures opposite the 
free diameter of your projection lens until you find the 
figure most nearly corresponding to its working distance, 
and at the top of that column will be the distance the center 
(point midway between the lenses) of the condenser must 
be from the aperture in order to allow the entire light beam 
to enter the projection lens. 

For example: Suppose the working distance to be 5 inches, 
and the projection lens aperture 2.5 inches. In the 15th 
space from the top in the left hand column of Table No. 8 
we find 2.5, and in the 11th column to its right we find 5. At 
the top of column 11 we find 18, which means that under the 
condition of working distance and lens diameter given, we 
must have 18 inches from a point midway between the’two 


MANAGERS AND PROJECTIONISTS 


195 


condenser lenses to the aperture in order to get the entire 
light beam into the projection lens. 

If the working distance had been 5.5 instead of 5, then the 
right distance would be 18.5 inches, because the next working 
distance given opposite the 2.25 lens diameter is 5.437, which 
is practically 5.5 inches, and at the top of this column we 
find 19 inches. Since 5.25 is half way between 5 and 5.5 we 
would split the difference between 18 and 19, w T hich would be 
18.5 inches. This would, however, have but slight effect, 
since when we get back as far as 18 inches, an extra half 
inch further alters the angle but very slightly. Nevertheless, 
while we are doing the job we might as well do it with pre¬ 
cision, therefore under that condition 18.5 would be the 
distance. 

CAUTION.—And now let us caution you that right here 
judgment and common sense enter. If your projection lens 
has an aperture of 2.25 inches or less, and it is necessary to 
retard the condenser to a greater distance than say 18 or 19 
inches in order to get the entire beam into it, it would be 
better practice to get a lens of larger diameter, because re¬ 
tarding the condenser calls for a condenser of longer focal 
length (E. F.), which operates automatically to place the 
crater further away from the collector lens, thus weakening 
the light collecting power of the collector lens, or in other 
words the total light available to the spot, see Fig. 36-H, page 
162. 

It is therefore for the projectionist to determine when and 
where retarding the condenser should cease in favor of in¬ 
creasing the projection lens diameter. 

Of course where the projection lens is already of maximum 
diameter, there is then the choice of retarding the condenser 
or reducing its free opening because we must secure evenness 
of illumination at the screen, even though there be actual 
light loss in the process. 

Personally we believe that up to say 18 inches it is better 
to increase condenser distance than lens diameter, especially 
if the projector is considerably out of center with the screen, 
provided the projection lens free aperture be already not less 
than 2 inches, but if the beam cannot be made to enter a 
2-inch aperture lens with a distance of 18 inches, then it is 
better to seure a projection lens of larger aperture than to 
set the condenser as far back as may be necessary to get 
all the beam into the lens. In this we of course assume that 
projection lenses of desired diameters can be had, which is 


{ DISTANCE CENTER OF CONDENSER OFAPERTURE } 9 


HANDBOOK OF PROJECTION FOR 


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PROJECTION LENS DIAMETERS 


Table No. 




































MANAGERS AND PROJECTIONISTS 


197 


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IN FIRST COLUMN 


Table No. 






































198 


HANDBOOK OF PROJECTION FOR 


not always the case, since such lenses are not made in 
aperture diameters greater than twice their focal length of 
the lens. Thus: A 4-inch E. F. projection lens cannot be had 
in greater diameter than 2 inches, and in practice it is doubt¬ 
ful if you could get one of quite that aperture. P. 139 and 148. 

UNIVERSAL METHOD OF SELECTING AND ADJUST¬ 
ING PROJECTOR OPTICAL SYSTEM. IMPORTANT 
FOREWORD AND EXPLANATION. In what follows the 
projectionist may not, and probably without this explanation 
would not understand why he is directed to first make diagram 
58 according to the diameter of his present projection lens 
and then, after applying diagram' 58 A, to again apply dia¬ 
gram 58, using the diameter of the new lens as its foundation. 
He will most likely ask why he could not as well apply dia¬ 
gram 58 A at once, and then apply diagram 58 without bother¬ 
ing with the first application of diagram 58 at all. 

The reason is just this: The available projection lenses are 
strictly limited as to diameters, and it is not at all certain that 
the projectionist will be able to get the diameter he should 
have. If the projectionist were to find by application of 
diagram 58 A and table No. 8 that a lens of the required 
diameter cannot be had, he is stuck, or will probably think he 
is, but if he has first applied diagram 58 he knows what the 
line-up for his optical system AS IT ALREADY IS should 
be, and it is important that he have the correct adjustment 
and correct condenser combination even though he cannot 
have the correct projection lens diameter. 

The first application of diagram 58 is to show what con¬ 
denser combination, and what distance from condenser to 
aperture you should have with the projection lens you are 
using. 

You then apply diagram 58 A and table 8 to find what 
diameter projection lens you must have to work efficiently, 
and then, when you have secured the right lens (if you are 
able to), you apply diagram 58 again to see what condenser 
combination and what distance you should have from con¬ 
denser to aperture for the new lens. 

With this explanation let us proceed with instructions for 

APPLYING DIAGRAM Figure 58. By means of table No. 
8. we have shown you how to ascertain what distance is neces¬ 
sary between center of condenser (point midway between the 
two lenses) and aperture in order that your projection lens 
admit the entire beam of light from the aperture. Let us now 
go a step further and, by means of Fig. 58 and 58A, exam- 


MANAGERS AND PROJECTIONISTS 


199 


ine and apply what amouts to a universal method for selecting 
condenser of proper focal length, correct distance center of 
condenser (point midway between lenses) and proper pro¬ 
jection lens diameter. 

In Fig. 58 you are to draw each line in its alphabetical 
order, and make each measurement in its numerical order. 

First, on a perfectly smooth, flat table top, spread a sheet 
of heavy paper suitable to make a drawing on. Light colored 
wrapping paper, which may be had almost at any store, will 
do very well, though it will be well to get a kind which will 
not tear too easily, because you will probaby wish, to retain 
the drawing as a permanent, or at least a semi-permanent 
part of your projection room records. Fasten the paper down 



securely, preferably with draftsman’s thumb tacks, though of 
course ordinary tacks will do. 

Have the following tools ready: A perfectly straight 
straight edge not less than two feet long. (A) An ordinary 
carpenter’s steel square will do nicely. (B) A pencil sharpened 
to a long, slim, flat point. (C) A draftsman’s triangle for the 
purpose of getting lines exactly at right angles to each other, 
though a carpenter’s steel square will serve very well, and 
two such squares will be excellent. (D) A ruler—the square 
will serve, if you have one. (E) An ordinary pair of com¬ 
passes, such as draftsmen use or such as carpenters use. 
You can make one that will serve very well with two sticks 
fastened together at one end with a screw and a pin or needle 
fastened to each of the other ends. 

FIRST.—Draw line A, Fig. 58. 

SECOND.—Draw line B, Fig. 58, exactly at right angles to 
line A, and near its right hand end. 

THIRD.—Measure distance from your projector aperture at 
film plane (position occupied by film) to first surface of pro- 









200 HANDBOOK OF PROJECTION FOR 

jection lens—in other words the working distance—when the 
lens is so adjusted that the picture is in sharp focus on the 
screen, and at that exact distance from' line B draw line C, 
also at exact right angles to line A. 

FOURTH.—Measure the exact free diameter, or opening of 
your projection lens, and at a point on line B distant from 
line A the exact diameter of the opening of your projection 
lens, make a mark. This mark is indicated by the lower point 
of arrow 2, Fig. 58. 

FIFTH.—On line C make a dot one inch below line A. This 
measurement is indicated by arrow No. 3. 

SIXTH.—Through these two points draw line D, as shown. 

SEVENTH.—Draw line E at right angles to line A, and at 
the point where lines A and D are exactly 3.75 (3J4) inches 
apart, measured vertically. This measurement is indicated by 
arrow No. 4. 

EIGHTH.— 1 % inches above and 1 % inches below line A 
make a mark on line E. These measurements are indicated 
by arrows Nos. 5 and 6. 

NINTH.—On line C make a mark 1.25 (1J4) inches below 
line A. This measurement is indicated by arrow No. 7. 

TENTH.—Draw lines F and G, as per diagram, joining the 
intersection of lines A and E and the lower end of arrow 7 
and the intersection of lines A and C and the lower end of 
arrow No. 6. 

ELEVENTH.—Measure the narrowest diameter of your 
positive carbon crater and, having set your compass to that 
measurement (you may do it with a ruler, but a compass is 
much better), find the point on line A where the vertical dis¬ 
tance between lines A and G is exactly equal to the crater 
diameter and make a mark on line A at that point, drawing 
line H from the point on line E at upper end of arrow No. 5 
through the point on line A and on across lines G and F. 

TWELFTH.—The distance from line E to the crossing point 
of lines H and F will be the focal length of each condenser 
lens required. For instance: If the distance from line E to 
the crossing point of lines H and F be 7.5 inches, then two 
7.5 piano convex lenses will be required. 

NOTE. —The combination may, and should be modified as 
follows: Use a 6.5 inch focal length collector lens and add 
the difference to the focal length of the converging lens, thus: 
Suppose the diagram calls for two 7.5 inch lenses. We install 
a 6.5 piano convex collector lens, which is one inch shorter 
focal length than is demanded. We then add one inch to the 
focal length of the converging lens, installing an 8.5 instead 


MANAGERS AND PROJECTIONISTS 


201 


of 7.5. Our condenser then is a 6.5 collector and an 8.5 con¬ 
verging lens. The E.F. of a 6.5 and an 8.5 lens is the same as 
that of two 7.5 lenses. 

THIRTEENTH.—The distance from line E to line C will 
be the correct distance from center of condenser combination 
(point midway between the two lenses) to projector aperture. 

FOURTEENTH. IMPORTANT.—It must be understood 
that the foregoing is the correct line-up for the projection 
lens you have in actual use at the time, and that the condition 
may or may not be efficient. YOU MUST NEXT determine 
what would be the correct (efficient) projection lens diameter 
under the existing conditions. To do this make a diagram as 
per Fig. 58 A, which you should keep as a permanent part 
of the projection room equipment. 

____ -3 

Vi" . t | r | 

ao 7? 7? n U /y 7y ts 7S ti 7<r 

Figure 58 A 

Line A, Fig. 58 A must be perfectly straight, and exactly 
ten inches long. Divide it into inch lengths, by means of dots 
on or lines drawn across line A, and number the divisions from 
10 to 20, as shown, the 20 being always at the left hand end 
of the line. 

Next draw line B, its left hand end exactly inch from 
line B and the right hand ends spaced exactly $/% of an inch. 

Now select one of your positive craters which is of average 
size, and measure its exact diameter the most narrow way. 
Set a compass with its points spaced apart the exact distance 
equal to the crater diameter (compass is not really necessary, 
but by using' it you will get more accurate results) and find 
the point at which lines A and B, Fig. 58 A, are spaced exactly 
that distance apart. The distance indicated is used in con¬ 
junction with table No. 8, as follows: 

Let us assume that the crater diameter fits the spacing of 
lines A and B at a point exactly over 16. We find the column 
in table 8 which is headed “16,” glance down it until our work¬ 
ing distance is reached, and then to the left hand column to 
get the correct lens diameter. 

The next move is to purchase a new projection lens, or 
lenses, as nearly as possible to the diameter indicated by 
table No. 8. Next make- an entirely new diagram as per 
Fig. 58, using the diameter of the free opening of the new 









202 


HANDBOOK OF PROJECTION FOR 


projection lens for the measurement indicated by lower point 
of arrow No. 2, Fig. 58. Otherwise the original instructions 
for making diagram Fig. 58 are not in any way changed. 

NOTE. —If it is not possible to secure a projection lens of 
the diameter indicated by table No. 8, it must be remembered 
that if your present lens is too small, then any increase in 
diameter will result in a more economical operation in that 
it will cause the transmission of a greater percentage of the 
light to the screen and will give a more even illumination of 
the screen, hence the effect of greater depth to the picture, 
always provided the optical system be re-aligned to fit the 
new lens diameter, as per instructions given. 

WARNING.— Diagram Fig. 58 must always be drawn to fit 
the diameter of the projection lens you are now using, regard¬ 
less of whether the lens is as large as indicated by Fig. 58 A 
and table No. 8 or not. 

When we have finally determined what focal length lenses 
are required, we go a step further. A 6.5 collector lens will 
reduce waste between the two lenses of the condenser to a 
minimum, hence we install a 6.5 collector lens in all cases, 
adding the difference to the focal length of the converging 
lens. Thus: Suppose we find that two 8.5 focal length lenses 
are necessary. We establish a 6.5 collector lens, which is 
(8.5 — 6.5) 2 inches, less than the focal length required. We 
therefore add 2 inches to the focal length of the converging 
lens, which makes it a (8.5 + 2) 10.5 lens, so that the actual 
requirement is a 6.5 collector and a 10.5 converging lens, 
spaced not to exceed 1/ 16th of an inch apart. The E. F. of 
this combination will be the same as the E. F. of two 8.5 
inch lenses. 

FOR SIXTY AMPERES OR LESS. —We would advise the 
use of the lens chart, page 191. The use of the diagram 
Fig. 58 is not advised for anything covered by the lens chart, 
since the charts are accurately worked out, whereas there is 
always the possibility of error when using the diagram, es¬ 
pecially by those unaccustomed to making drawings and 
working to fine measurements. 

The use of the diagram Fig. 58 sounds quite complicated, 
but it is really very simple indeed, if followed through step 
by step. 

WARNING.—Projectionists and exhibitors are warned that 
unless the various elements of the projector optical system 
be intelligently selected and carefully and intelligently ad- 


MANAGERS AND PROJECTIONISTS 


203 


justed with relation to each other the best results will not 
be had on the screen. There will not only be waste of light 
but unevenness of illumination of the screen, with consequent 
loss of depth, or stereoscopic effect. 

CONDENSER DIAMETER.— The diameter of the con¬ 
denser has an immediate and a very important bearing both 
upon the amount of light available to the screen from a 
given amperage, and upon its quality. 

The large diameter (4.5 inch) condenser in almost universal 
use in the United States and Canada has very much greater 
light collecting power than has the small diameter (3 and 3.5 
inches) condenser used in some other countries. As com¬ 
pared with a 3-inch lens the 4.5 inch diameter condenser has 
just about 2 times the area. At first glance we would be in¬ 
clined to say the spialler lens would, nevertheless, have the - 
greater proportional collecting power because the strongest 
light flux passes through the center of the lens, but in this 
we would be either entirely in error, or partially so, because 
while it is true the strongest light flux strikes at approxi¬ 
mately the center of the collector lens, if the crater angle be 
correct, still the greater area of the outer zones of the col¬ 
lector lens much more than compensate for this, which makes 
the collecting power of the outlying zones of high value, or 
would make them of high value were the quality of the light 
the same for all zones. 

The fact is, however, that while the light source delivers 
light of equal quality to all zones of the collector lens, the 
heavy angle at which it reaches the outer zones sets up a 
tendency to chromatic aberration. 

The colors thus produced are carried down into the center 
of the light beam at the spot by spherical aberration, thus re¬ 
ducing the whiteness and brilliancy of the entire spot. 

There is, therefore, something more than a possibility that 
the smaller diameter condenser may after all be as efficient, 
if not even more so than the standard 4.5 diameter now in 
use, especially in view of the fact that the crater may be 
established nearer to the smaller, thinner lens. 

Then, too, there is another phase of the subject to be con¬ 
sidered, viz., the condition which in itself prevents the use of 
the full diameter of a standard 4.5 inch condenser. Fig. 59, A 
is the drawn-to-scale diagrammatic representation of an 
ordinary plano-convex 4.5 inch diameter condenser, having 
an actual 4.25 inch free opening, its front surface located 16 
inches from the aperture. The projection lens has a working 


HANDBOOK OF PROJECTION FOR 



Figure 59. 


distance of 6 inches and 
a free opening of 2.25 
inches. 

Examining diagram A, 
Fig. 59, we readily see 
that, except for light 
carried down into the 
effective beam by spher¬ 
ical aberration, no light 
from the condenser zone 
labeled “lost light” can 
possibly enter the pro¬ 
jection lens under the 
conditions shown. It is 
therefore a fact that un¬ 
der this condition the 
diameter of the con¬ 
denser may be reduced 
without loss of screen 
illumination, provided the 
reduction of diameter be 
not carried beyond lines 
X-Y of the upper dia¬ 
gram. In fact the re¬ 
duction will serve a good 
purpose, as before set 
forth, in making the re¬ 
maining beam more 
white and brilliant at the 
film plane. 

In diagram B, Fig. 59, 
we see the condenser 
diameter thus reduced 
by means of a diaphragm 
which eliminates the 
outer zones of the con¬ 
denser, reducing it to a 
diameter which enables 
the projection lens to re¬ 
ceive its entire beam. In 
the condition set forth 
by diagram A, Fig. 59, 
the light from the outer 
condenser zones is worse 













205 


MANAGERS AND PROJECTIONISTS 

than wasted, for the above reasons, and for the further 
reason that, as has already been set forth (see page 182) 
this condition causes unevenness of illumination on the screen, 
with accompanying loss of picture depth. 

This whole matter forms an interesting field for future 
study and investigation by projectionists and projection en¬ 
gineers. It is one in which the projectionist using heavy 
amperage is especially interested, but the local condition 
must always govern, and whether it is best to reduce the 
condenser opening, increase the projection lens diameter or 
utilize the entire ray by applying diagram 58, is something the 
individual projectionist must decide for himself. 

Everything considered we incline to the opinion that the 
better procedure would be to equip projectors with a standard 
4.5 inch diameter condenser, and to add an iris diaphragm 
by means of which the projectionist may reduce the con¬ 
verging lens opening to fit the local condition. 

LARGE DIAMETER CONDENSERS. —Attempts have been 
made by those not well grounded in projection optics to use 
a large diameter condenser. A lens even as large as 6.5 
inches has been experimented with. It is, of course, quite 
entirely possible to use such a lens, but in order to use it 
efficiently the condenser would have to be a great distance 
away from the aperture. This would mean a long focal length 
condenser, and the light source would have to be located a 
considerable distance from the face of the collector lens. In 
fact, while we have made no actual experiments to determine 
the matter, we believe that in using the large diameter con¬ 
denser the necessarily greater distance of the light source 
from the face of the collector lens would just about be com¬ 
pensated for by the increased diameter of the lens. 

On the other hand a lens of this diameter would be com¬ 
paratively thick, and much more costly! The necessarily 
greater distance employed between a lens of this diameter 
and the aperture would make the projector an unwieldly piece 
of apparatus, which could not be housed in the average pro¬ 
jection room as now constructed. Everything considered it 
is quite safe to say that future procedure will in all human 
probability tend toward a reduction in condenser diameter 
rather than an increase. 

AERIAL IMAGE—WHAT IT IS— The aerial image of the 
condenser i§ an image of the front surface of the converging 
lens which jj present at a certain point in the light beam, 


206 


HANDBOOK OF PROJECTION FOR 


It is made visible if a suitable screen be held in the light 
beam at the proper distance from the projection lens. 

REVOLVING SHUTTER— The revolving shutter (see page 
611) can hardly be termed anything else than an integral 
part of the optical system of the projector, since it works 
in direct conjunction therewith. Its presence, or rather the 
necessity for its presence, operates to prevent the use of 
projection lenses of very large diameters. It is not our pur¬ 
pose at this particular place to go deeply into the treatment 
of the revolving shutter in all its various phases (see page 
611), but merely to give you the effect of distance of the 
shutter from the projection lens. 

The shape of the light ray in front of the projection lens 
varies with the local condition. In the case of a very short 
focal length projection lens the beam may emerge from the 
projection lens divergent, the amount of divergence de- 



Figure 60. 

pending upon the focal length of the lens, or put in another 
way, upon the projection distance and the width of the 
picture. With very long focal length lenses the aerial image 
may be a considerable distance in front of the projection lens, 
and between the lens and the image the ray may be either 
parallel or even slightly converging. The correct position 
for the shutter is at the aerial image, if it is practical to 
place it there. The position of the aerial image may be de¬ 
termined in a number of ways. It may be found by holding 
a bit of dark colored paper in the light ray, moving the 
paper back and forth until a sharp image of the condenser 
is obtained. When the image is at its sharpest the paper is at 
the position of the aerial image. Another method is to place 
a circle of sheet metal or cardboard, in the center of which 
a hole x /\ of an inch in diameter has been drilled, against the 
face of the converging lens. Then, first having opened the 



MANAGERS AND PROJECTIONISTS 


207 


projector gate and turned the revolving shutter until the lens 
is open, project the light through and blow smoke in the 
beam in front of the projection lens. 

A point will be found where the light beam will narrow 
down as per Fig. 60, and the narrowest point of the ray will 
be the plane of the aerial image. If a cardboard disk is used 
against the condenser you must work fast when making this 
test, else the cardboard may get hot, smoke and dirty your 
lens. 

Still another method, and perhaps the quickest and best one, 
is to project the white light to the screen and then pass a 
piece of metal or cardboard downward through the light 
beam in front of the projection lens. If the obstruction is 
between the lens and the aerial image the shadow will show 
first at the bottom of the screen, but when the obstruction 
is made near the position of the aerial image a shadow will 
appear from both directions, and when these shadows meet 
exactly in the center of the screen you are obstructing the 
beam at precisely the plane of the aerial image. 

And now, frankly, here is a point on which we are not yet 
altogether certain. If the beam be parallel from the lens 
to the aerial image there are those who hold that the re¬ 
volving shutter may be placed at any point between the lens 
and the image with equally good results. We, however, hold 
that the point of the aerial image is better, because at that 
point a dissolving effect is had, and we believe that this dis¬ 
solving effect will enable the projectionist to trim down his 
master blade somewhat more than can be done if the shutter 
be placed at any other point, even though the diameter of 
the ray at the other point be equal with the diameter of the 
ray at the aerial image. We do not make this statement 
of absolutely known fact, but only as our opinion in the 
matter. 

Note : Under some conditions the aerial image will have 
greater diameter than the beam at a point nearer the lens. 
When this is the case it probably will not be advisable to 
place the shutter at the aerial image. First find out what 
your conditions are and then use judgment and common 
sense. 

The only benefit in locating the revolving shutter at the 
narrowest possible point of the light ray, usually the aerial 
image, is that at that point it is possible to reduce the width 
of the master blade of the revolving shutter to its lowest 
possible value, thus allowing the passage of the greatest pos- 


208 


HANDBOOK OF PROJECTION FOR 


sible percentage of the light, and also probably securing a 
better optically balanced revolving shutter. 

PROJECTION LENS DIAMETER AND REVOLVING 
SHUTTER— Any increase in working diameter of the pro¬ 
jection lens calls for an immediate increase in the width of 
the master blade of the revolving shutter. This is true even 
though the smaller lens accommodated the entire light ray, 
unless the larger lens be diaphragmed down, since that part 
of the diameter of the lens which is not working will pro¬ 
ject a halo of reflected light, and that light is often suffi¬ 
ciently strong to cause faint travel ghost unless it be cut off 
by the revolving shutter. That portion of the edge of the 
revolving shutter master blade which intercepts light ray 
runs at a certain given speed at the point it intercepts the 
light beam, the speed being, of course, dependent upon the 
distance of the center of the light beam from the center of 
the shutter shaft. If the light beam be 1.5 inches in diameter, 
it follows that it will take the edge of the shutter blade 
traveling at a given speed a longer time to cut through the 
beam and obliterate the picture from the screen than it would 


OBdFCT PIM£ 


LEM-SPimF 


/M6BPIME 


££. 








-*r- 




Figure 61. 

if the beam were only one inch in diameter, and if the beam 
be 2.5 inches in diameter there is a decided difference in the 
time requirement as against the beam 1.5 inches in diameter. 
It must be remembered that in any event the revolving 
shutter eliminates approximately 50 per cent, of the total 
light passing through the aperture. This does not mean that 








MANAGERS AND PROJECTIONISTS 


209 


50 per cent, is eliminated by the master blade, but by the 
master blade and the other necessary shutter blades. It is 
highly desirable to get all the light through to the screen 
that it is possible to get without setting up travel ghost or 
other injurious effects, therefore the projectionist should study 



his local condition carefully and ascertain any possibility 
there may be for improvement through altering the distance 
of the revolving shutter from the projection lens. We can¬ 
not well do more than give you an outline of the problems 
involved, because as we said in the first place, local con¬ 
ditions vary so much that the projectionist himself must be 
depended upon to determine what is best in his own indi¬ 
vidual case. However, unless he himself thoroughly under¬ 
stands the problems involved he cannot do this and will in 
consequence probably have his revolving shutter working 
inefficiently as regards the amount of light delivered to the 
screen; also he very possibly will have a worse condition as 
regards flicker than he need have. 

TO TRACE LIGHT RAYS THROUGH LENSES.— We 
may be criticised for attempting to teach the projectionist 
such things as this. If so we have no apology to offer. The 
projectionist is forced to use directed light—rays directed by 
lenses—in his profession. The steam engineer who does not 
understand the action of steam, and who could not trace its 
action under any given set of ordinary circumstances, would 
be immediately set down as an ignoramus. He would be 









210 


HANDBOOK OF PROJECTION FOR 


ridiculed by his brother engineers, and rightly too. He uses 
steam. He should understand it. The projectionist uses 
lenses and refracted light. He should understand them. 

More and more we are becoming convinced that there is 
no more real mystery about light action than there is about 
steam. Opticians like to make a mystery of their profession. 
It is remunerative for them to do so. They insist that even 
the most simple problem in light action be worked out by a 
very wonderful and intricate process. 

John Griffith has evolved a method of tracing light action 
through lenses which we would ask that you examine with 
an open mind, remembering that, as Griffith aptly says, while 
it may not be scientifically correct, it nevertheless IS PRAC¬ 
TICAL; also, it is a thing any of you may understand and 
apply in practice. 

GRIFFITH’S PLAN. —By experience we have found that 
approximately correct results may be obtained when a set 
of simple lenses, such as a condenser combination, is under 

s\ 



S//0U///YO r//£ 7r>£Ffr/?Cr/ON /? jBOMUJ? O/T rffsTOOC# 
O/vs £o/nr of 

Figure 63. 


consideration, by considering the center of power of the lens, 
or the combination, as being a single plane. 

Let us, for example, select a bi-convex lens. In scientifically 
correct procedure there are two planes from which meas¬ 
urements should be made, but we may, nevertheless, for the 
sake of convenience, consider the center of the lens as a 
single plane from which a single measurement may be made. 
True, there will be some error incident to this method of 









MANAGERS AND PROJECTIONISTS 


211 


procedure, but it will be negligible as compared to the error 
due to spherical aberration. 


The same plan applies to a plano-convex condenser com¬ 
bination. There are in fact two distinct planes from which 
measurement should be made, but a single plane located at a 



position between the two real planes which will vary with 
the radius of the convex surfaces of the lenses, will serve. 
This plane will be nearest the surface having shortest radius. 

Very unscientific, yes, but it is practical, while the scientific 
method of two measurements is not practical, unless spherical 
aberration be taken into account, a thing we have yet to 
see any of the scientific men even attempt to do. 

There are 2 rules in optics to which attention is directed, 
viz.: (A) When the object and image are both located at a 
distance from the lens plane equal to twice its E. F. they 
will be equal in size. (B) The relative size of object and 
image are in proportion to their respective distances from 
the lens plane. 

It may be assumed that most opticians are familiar with 
the wording of these rules, but how many of them have 
reasoned out what the rules really mean? How. many of 
them realize that rule A means that, no matter where the 
object and image may actually be, there are always two 
planes, located a distance equal to 2 times the E. F. of 
the combination (or the focal length if it be a single lens) 
on either side of the lens plane, and that these planes are 
exact duplicates of each other, except that one is inverted. 
Yet if rule A is correct, this must be true. By this we mean 
that if a ray passes through or reaches a certain point in 
the image plane (see Fig. 62) after refraction, its incident 







212 


HANDBOOK OF PROJECTION FOR 

direction must be along a line which will pass through the 
point in the object and a point in the object plane (see Fig. 
61) the same distance from the optical axis that the re¬ 
fracted line passed through the image plane, although the ray 
may actually have its origin on either side of the object plane 
and at any practical distance from the object plane. 

It is thus seen that if we desire to trace the path of any 
particular ray in a diagrammatic way, as illustrated in Fig. 
62, we would first ascertain the E. F. of the combination, or 
the focal length if it be a single lens, and would establish 
lines A-B, Fig. 62, distant from the lens plane by twice the 
E. F. or focal length of the lens combination. We would 
then draw a line through a point of the source to some 
point of the lens plane and would continue the line to the 
object plane. If we then draw broken line D, Fig. 62, 
joining points E and F, and continue it through the image 
plane line, we have but to draw a line from the point where 
line G joins the lens plane, to and through the point where 
broken line D joins the image plane, to have the direction 
of the refracted ray, which will continue in that exact 
direction until it is intercepted. 

Fig. 61 shows how to lay out the diagram, both object and 
image planes being twice the E. F. of the lens from the lens 
plane, and parallel thereto. Fig. 62 shows how a single ray 
is refracted. 

Fig 63 shows how a bundle of rays are refracted, and Fig. 
64 illustrates the method of finding the image of any point 
of the object. 

First draw line 1, Fig. 64, through a point in the object, 
and continue it until it joins the object and lens planes. 
Having thus established the point in the object plane, we 
next draw a line from it to the image plane, so that it passes 
through the optical axis line at the lens plane. This is 
line No. 2 in Fig. 64, and gives us the point of the image 
plane through which the refracted ray, 1-R, Fig. 64, will 
pass, whereupon a line, No. 3, Fig. 64, drawn through the 
object point and the lens plane at the optic axis, and on to 
the point where it meets refracted ray 1-R will indicate the 
image point. The terms Object and Image planes are used 
merely to identify the planes as shown in Fig. 61. And it 
should be distinctly understood that the object and image 
plane herein referred to have nothing to do with the position 
of the actual object and image. 

It will apply to either single lenses or simple combinations. 


MANAGERS AND PROJECTIONISTS 


213 


Projection 

U NDER the broad term “projection,” many things are 
grouped. After the work of the actor, the director, 
the cameraman and all those other various ones hav¬ 
ing to do with the production of the photoplay is finished, 
the product only has commercial value when it is finally 
presented to the public on the screen. 

Presentation of the photoplay and projection of the photo¬ 
play are terms with entirely different meanings. Projection 
includes only those actual things necessary to the placing 
of the picture on the screen. Presentation of the photoplay 
includes its projection and all those various things which go 
to (a) make the theatre patron comfortable ; (b) to properly 
synchronize appropriate music with the picture ; (c) to make 
the surroundings pleasing; (d) to make proper lighting of the 
auditorium, and in fact all those various things which go to 
make the finished whole pleasing to the audience. 

It is only with projection that we are, however, concerned. 
We believe there are very few who realize to what an extent 
the whole motion picture industry rests on the final act of 
projection. It may be stated as an incontrovertible fact that 
the success or failure of any photoplay, insofar as concerns 
any individual audience, will to a very considerable extent 
rest upon the excellence of its projection. We do not believe 
any person conversant with the facts will dispute the state¬ 
ment that inferior projection will mar the production—make 
it less pleasing to the audience. Nor do we believe anyone 
will dispute the proposition that the more pleasing the 
screen results, entirely aside from any merit it may have as 
a play, or the “pulling power” of the artist therein, the 
greater will be the patronage of the theatre. 

On the other hand certainly no one will even question the 
statement that a dim, “fuzzy,” unsteady projection of a 
photoplay will be far less pleasing to an audience than will 
a perfect projection. 

Most of the readers of this book have visited theatres 
where the projection is very good indeed, and have also 
visited theatres where the projection is very poor indeed. 
You all know what the relative effect of those two conditions 


214 HANDBOOK OF PROJECTION FOR 

would be as applied to any given production—what effect it 
would have on the “pulling” power at any given theatre. 

Summed down, this all means that careful, intelligent work 
in the projection room brings added dollars in the box office, 
and unintelligent, slovenly work in the projection room means 
less of money to the box office. 

To put perfect projection on the screen and keep it perfect 
during even one entire reel requires ability and knowledge. 
It also requires ceaseless vigilance and artistic sense of 
high order. 

Not only must the projector mechanism and optical train 
be kept in perfect condition, but also all other machines and 
projection room equipment must be maintained in like con¬ 
dition. 

The actual mechanical knowledge required to accomplish 
this is considerable, the necessary electrical knowledge 
covers a wide range, and the optics of projection are quite 
sufficient to keep any man busy studying for an extended 
period of time. 

As a matter of fact the modern high class projectionist 
must have comprehensive electrical knowledge covering 
dynamos, motors, transformers, mercury arc rectifiers, wire 
systems, magnetic action and many other things. He must 
have an accurate knowledge of the electric arc and its action. 
He must be a mechanic of no mean ability, because he is 
handling a high speed mechanism which must be accurate 
in its vital parts within 1/10,000 th of an inch. He must have 
a very good grounding in optics, and must understand lens 
action thoroughly. In addition to all this he must be able 
to judge naturalness of action in any moving object. 

REDIRECTS PHOTOPLAY.— A no less person than D. 
W. Griffith is credited with having made the following state¬ 
ment: “The projectionist in a large measure is compelled to 
redirect the photoplay.” This is not intended as a verbatim 
repetition of Mr. Griffith’s words, but it is in effect what he 
is credited with having said. The statement attributed to 
Mr. Griffith is entirely correct, because by a change in the 
speed of projection the projectionist is enabled to alter the 
whole effect of any given scene, insofar as concerns the 
audience. For instance, a funeral procession projected at 
excessive speed becomes farcial and ridiculous. On the 
other hand, a race projected at a too-slow speed is absurd, 
These are two extremes, but the relative effect is there in 
any sort of scene projected at wrong speed. Actors an<J 


MANAGERS AND PROJECTIONISTS 


215 


actresses are paid huge sums on the presumption that they 
can enact a given scene in the most artistic way. Is it not 
then just plain common sense that the best possible effect 
will be had if the action of these artists be portrayed on the 
screen faithfully, exactly as they were in the original? 

The theatre manager often excuses over-speeding of pro¬ 
jection with the statement that he wants to “put pep” into 
his show. God in heaven! Imagine the manager of a “store 
room” theatre in Kalamazoo, Missouri, undertaking to “put 
pep into Clara Kimball Young or Mary Pickford, or im¬ 
proving on the. portrayal of a scene by Earle Williams or 
William Hart. Could anything be more ridiculous? Put in 
another way, when the theatre manager makes a statement 
of that kind he simply says in effect, “I know more about 
how that scene ought to be acted than does the artist who 
acted it and the director who planned it.” 

PROJECTION HAMPERED. —In all but a comparatively 
small number of theatres, projection is more or less ham¬ 
pered in various ways. First, there is the iron-bound, un¬ 
elastic “schedule,” from which the projectionist is not per¬ 
mitted to vary. The manager very naturally desires to start 
his show at a given time, and have it end at a given time. 
This is, of course, very necessary, but while the average 


■K°te(D twe TlME PERR-eev_is> approximate, s' \ tfore (3) when running 4k‘ v 5k. show$>begin 

AND BE VARIED BY PROJECTIONIST, BUT THE / ZX \ WITH FEftTURE.MftHINC, TIME ASSCHEDULEI 

time per. Show, must BE kept within q2to11rmI when running, 64shows se^in withthE 

SHOWM V^V PtATORE. PROVIDED THERE RRE NOT MORE 

Note IZ) >p suoes rr.e used thetime. v ^ than 5 reeus to feature. 

ISINttllOEO IN TH6 6HOH). TIME PER. SHOW 



3Hks..4CMin 

£j4rs.45Mih 

2Has.27Min 

2H*s 12 Min 

2. H Rb 

1 Hr-SOMih 

IHr.-4IMin. 

IHr-34Min 

1/5 

_) 

U 

Li 

cc 

r 

1200-340 

34°-720 

7.20-1100 

1200-245 
245-530 
530-815 
6 15-H-oo 

;2.oo-|. ia 
112-3.35 
339-6.06 
6.0 6-839 
839-11.00 

1200-2.12 
2.12 424 
424-6-36 
63S-846 
848-11-00 

12004.00 

foo-500 

3.00-5.00 
5.00-700 
700-3.00 
3.004 i oo 

1200450 

1.50-3.40 

340-530 

530-720 

7 20-9 IO 
910-1100 

12.0042.54 

1254-2.35 
2.35-4-16 
4.16-557 
557-7.38 
738-9.13 
9.13-11.00 

12.00-1 36 

136-310 

3.10-444 

444-618 

6-18-752 

752-326 

926-11.00 

3)shows 

4)shows 

J-e) shows 

:5)shows 

S^SHOWS 

</5 

1 

i 

is y shows 

7)SHOWS 

(7) 

— 

— 

— 

— 

— 

»5.7 

145 

135 

(0) 

— 

— 

— 

16-5 

15 

13.7 

127 

118 

(3) 

1" 

— 

163 

147 

»3.3 

12.2 

113 

10.5 

iqgi — i 

— 

146 

13.2 

1 2 

II 

»0v| 

94 

m 

! — 

15 

133 

12 

10-9 

IO 

9.2 

8.5 


— 

13.7 

122 

II 

IO 

9.2 

8.5 

— 

m 

— 

12.7 

M-3 

I0| 

3-5 

85 

— 

— 

m 

15-7 

11.8 

105 

9.4 

8.5 

— 

— 

— 

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14.6 

II 

97 

88 

— 

— 

— 

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— 

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12.9 

9.7 

8-6 

— 

— 

— 

i 

— 


TIME PER. REEL IN MINUTES 


L DflVtS IBl E |04-S.T. NXC 


Figure 64A. 


































216 


HANDBOOK OF PROJECTION FOR 


manager wants the result, he is not willing to do the pre¬ 
liminary work necessary to enable the show to be run to 
schedule without injury. In Fig. 64A the effect of certain 
things is visualized. In this diagram, which is the work of 
L. Davis, projectionist, New York City, we see the effect of 
running to schedule with varying footage. For instance, 
having a seven-reel show, lasting one hour and fifty minutes, 
it will be necessary to run at an average of 15.7 minutes to 
the reel, whereas if the number of reels be increased to 
9 then the speed would be an average of 12.2 minutes to the 
reel. And right there comes the abuse of the schedule. The 
manager has a fixed schedule of, let us assume, 2 hours. To¬ 
day he has a show of 8 reels, which will be an average of 
15 minutes to the reel, provided the whole time be given over 
to projection. But tomorrow an extra scenic is shoved in. 
The schedule remains fixed, but the time is, by this pro¬ 
cedure, automatically speeded up to 13.3 minutes per reel. 

Where a fixed schedule is employed, there is and can be 
but one proper procedure, viz: the show must first be pro¬ 
jected at proper speed, the required time for such projection 
noted, and enough taken from or added to the program to 
enable the projecting of the show at proper speed in the limits 
of the schedule. This is one of the big vlaues of tableau, 
orchestras and prologues. They can be utilized to fit the 
show to the schedule, which cannot always be done where 
the show is entirely photoplay. 

OVER-SPEEDING. —One of the cardinal sins of the the¬ 
atre is over-speeding projection. Former President Wilson 
once said, within hearing of the author: “I have often seen 
myself in motion pictures, and the sight has made me very 
sad. I have wondered if I really do walk like an animated 
jumping jack, or move around with such extreme rapidity as 
I appear to.” 

President Wilson did not know what caused it, but you 
and I do. It was over-speeding of projection. Over-speeding 
(a) increases the speed of action of all moving things; (b) 
sets up heavy strain on the entire projector mechanism and 
on the sprocket holes of the films. Over-speeding is repre¬ 
hensible from any and every viewpoint. It is practiced by 
managers and projectionists who have no respect for the 
property entrusted to their care and no adequate conception 
of the business of exhibiting motion pictures or of their duty 
towards their patrons. 

Over-speeding projection produces a ridiculous travesty on 


MANAGERS AND PROJECTIONISTS 


217 


the original, the amount of which will depend upon the rate 
of over-speeding. There are managers and projectionists 
who talk learnedly about aj reel requiring “15 minutes” or 
“18 minutes,” in blissful ignorance of the fact that their 
words convict them of having slight adequate knowledge of 
artistic projection. 

As a matter of fact in any given production the speed of 
projection is likely to vary with individual scenes, and, as 
a whole, with individual reels. 

The correct speed of projection is the speed at which each 
individual scene was taken, WHICH SPEED MAY, AND 
OFTEN DOES, VARY WIDELY. 

A cameraman out on location encounters bad light condi¬ 
tions. He slows down camera speed to the limit, in order to 
get all the light he can. The next scene to this was per¬ 
haps taken in a studio, with perfect lighting conditions and 
at maximum speed. One may have been taken at 60 and 
the other at 70. It requires no extraordinary brain power to 
understand that if the projector pounds along through both 
scenes at 69, one scene will be correctly portrayed and the 
other will be entirely too slow, or if the projector runs at 
70 one will be correct and the other entirely too fast. On 
the other hand, if the projector runs both at 65 then both 
will be wrong. 

One of the highest functions of projection is to watch the 
screen and regulate the speed of projection to synchronize 
with the speed of taking. 

Of course if cameramen always took scenes at one speed, 
all that would be necessary to perfect speed of projection 
would be to set the speed projector at camera speed, but 
the fact of the matter is THERE IS NO SUCH THING AS 
A SET CAMERA SPEED. Camera speed varies all the way 
from 60 to as much as 85. 

The projectionist who regards the finer details of pro¬ 
jection as not of sufficient importance to justify him in giving 
them attention is not, and in our opinion never will be, a high 
class man. Nor is the projectionist excused by the fact that 
many managers impose schedule limitations which render 
high class work impossible, or in other ways hamper his 
work. 

Many managers do impose conditions which render high 
class work impossible, but the fact remains that the man 
who persistently and consistently bends every energy to im¬ 
prove his projection in every possible way is, in the end, 


218 


HANDBOOK OF PROJECTION FOR 


bound to win. It may and probably will require considerable 
time ; it may be discouraging, but success will finally come, 
and with it, at least in some degree, financial reward. 

The manager who employs a high class projectionist, pays 
him an adequate salary, provides him with good working 
conditions, tools and supplies, and insists on high class pro¬ 
jection. may not immediately see the benefit. The fact re¬ 
mains, however, that in due course of time the public will 
recognize the fact that in a certain theatre they are sure to 
see a perfect screen result and other things being equal the 
effect of this will be made visible at the box office. 

We might expend pages in setting forth interesting and 
valuable matters pertaining to the broad subject of projection, 
but inasmuch as space is limited, and the whole book is 
really devoted to that subject, we will end by saying: 

Over-speeding the projector is an outrage on the public; 
an outrage on the producer; an outrage on the projector 
manufacturer; an outrage on the film exchange and an out¬ 
rage on the projectionist himself. There is and can be no 
excuse for it—absolutely none whatever. If the house is full 
and a crowd waiting to gain entrance it would be far better 
to eliminate one reel of the program than to butcher the 
whole performance. 


THE MAN WHO DOES NOT 
BELIEVE IN THE VALUE 
OF EXPERT KNOWLEDGE 
IS AN EXPENSIVE EM¬ 
PLOYE AT ANY PRICE. 



MANAGERS AND PROJECTIONISTS 


219 


The Screen 

T HE sole and only function of the screen is that of re¬ 
flecting “picture light.” The eye sees the picture pre¬ 
cisely for the same reason it sees any other visible 
object. Exactly as light rays are reflected from any visible 
object to the eye, so in projection light rays are reflected by 
the screen surface to the eye. The picture appears plainer, 
sharpr and in every way better if the picture light be abund¬ 
ant—the screen brilliantly illuminated—than if it be dull, or 
if light other than picture light be also reflected. 

The term “picture light,” as used here, may be under¬ 
stood as meaning, light projected to the screen from or by 
the projection lens; “other light” is light reaching the screen 
from sources other than the projection lens, which latter, 
being undirected by the lens, shines indiscriminately upon 
both whites and shades of the picture, thus dulling the con¬ 
trast and causing the blacks to appear gray. 

There is a great difference in screen surfaces and the re¬ 
sults had from different ones with a given intensity of 
picture light. This is likely to be especially true when the 
screen be viewed from various parts of an auditorium, but 
until quite recently there has been no dependable, authorita¬ 
tive data setting forth the characteristics of various sur¬ 
faces used for projection. The author had in mind the 
making of certain measurements and tests for this edition 
of the handbook, and had in fact already done considerable 
preliminary work thereon when the Society of Motion 
Picture Engineers made available tests of screen surfaces 
which made that work on our part unnecessary. We were 
well pleased with this, partly because of the tremendous 
amount of work involved in the making of such tests, but 
even more because such data should come from just such a 
source as the Society. We shall present the tests and the 
conclusions arrived at, page 259-267. They have real value in 
that they enable exhibitors and projectionists to work intelli¬ 
gently in the matter of selecting screen surfaces for audi¬ 
toriums of various depths and widths. 

A FALSITY. —In the past many exhibitors and projection¬ 
ists have based their judgment of the efficiency of various 


220 


HANDBOOK OF PROJECTION FOR 


screen surfaces on looking at the performance of screens in 
different theatres. 

This is an utterly unreliable test, because it almost never 
happens that there are two screens in neighboring theatres 
where the various factors which may affect the result are 
of equal value, and the working conditions precisely alike. 

In any two theatres the brilliancy of projection light may, 
and in all human probability will, have different value, 
because of differences (a) in amperage at the arc, (b) in 
crater angle, (c) in the carbons themselves, (d) in the con¬ 
densers or their spacing or discoloring, (e) in the general 
adjustment of the optical train, (f) in the projection lens 
diameter or working distance, and (g) in the revolving 
shutter. 

The result may also be very much altered by the decora¬ 
tions of the theatre, by its lighting, by the number and ar¬ 
rangement and power of the orchestra lights, by the screen 
surroundings, the screen border, the shape and height of 
the auditorium, size of the picture, angle of projection, etc., 
etc., through a long list. 

In fact the things affecting apparent screen brilliancy in 
any given theatre are so very many that the judging of 
relative screen values by observing the picture in various 
theatres is an utterly futile endeavor. 

It is even impractical to judge closely of values by sub¬ 
stituting one screen surface for another while a picture is 
running, because of possible differences in light values. Sup¬ 
pose we run half a picture on one screen and then drop an¬ 
other down to receive it, but the crater angle has, unknown 
to even the projectionist, changed, or the supply voltage has 
dropped, thus altering the light brilliancy considerably. 

The only way such a test can be made with any assurance 
of reliable results is to cover half the screen with the sur¬ 
face it is desired to test, and then project a picture, observing 
results from all parts of the theatre. 

This is a test which is in every way fair; also it is not a 
difficult one to make, but exhibitors and projectionists should 
remember that it is not to be expected that the surface of a 
screen which has been in use for a considerable time can 
enter into successful competition with a new surface. 

We would most emphatically warn exhibitors, projection¬ 
ists and theatre managers of the danger of judging hastily 
as between various screen surfaces. We would also caution 


MANAGERS AND PROJECTIONISTS 


221 


exhibitors, managers and projectionists against the too ready 
acceptance of statements made by screen salesmen. 

Those gentlemen are employed to sell goods. Their job 
depends upon their ability to do it, and we have known of 
cases where they did not confine their statements as to the 
merit of their own goods vs. the screens made by others to 
quite the exact facts. 

We have known of many cases where exhibitors have paid 
substantial sums of money for new screens which were in 
fact inferior for use in their theatre to the screen the new 
one displaced. In such cases the exhibitor might better 
have taken his money out and scattered it in the street. 

It is a part of the duty of projectionists to study screen 
surfaces and be able to advise the theatre management in¬ 
telligently in such matters. 

We would advise exhibitors to under no circumstances pur¬ 
chase screens until they have first carefully examined the 
various charts and tables herein contained, and ascertained 
the characteristics of such surfaces, subject only to later, 
amended data published from time to time in the projection 
department of the Moving Picture World. 

If for any reason it is not deemed expedient or advisable to 
follow the foregoing advice, then we would advise against 
the purchase of any screen until the maker or dealer has 
covered half your theatre screen with a sample of the sur¬ 
face he is selling. 

There is absolutely nothing impractical in the latter. It is 
quite possible for a screen salesman to carry a sample of 
that size. Once such a sample is in place it is very essential 
that the result be viewed from every portion of the house, 
including the balcony, if there be one. 

Don’t attempt to judge from a small sample. Unless you 
can determine the characteristics of the surface under con¬ 
sideration by the tables and charts submitted herewith, 
oblige the salesman to cover half your screen, or else escort 
him to the front exit and bid him a polite but firm good bye. 

As already set forth, the only function of the screen is to 
reflect light. It therefore follows that in order to under¬ 
stand the results emanating from any given screen surface 
we must first understand a few of the many laws which 
govern light action. 

SPEED OF LIGHT.— Light travels at the terrific speed of 
186,000 miles per second, a speed so tremendous that there is 
no way of controlling it, hence light speed has a fixed value 


222 


HANDBOOK OF PROJECTION FOR 


which cannot be altered. This item is of no particular in¬ 
terest to the projectionist, except as a matter of general 
information. 

REFLECTION; DIFFUSE, SEMI-DIFFUSE AND REGU¬ 
LAR.— There are three kinds of reflection, viz., regular, semi- 
diffuse and diffuse. Regular reflection occurs when light 
strikes a smooth, polished surface, and is not broken up and 
scattered. An example of regular reflection is the ordinary 
mirror, in which we see ourselves because light is reflected 
from the surface of our fact; to the glass, and by the glass 
is reflected back into our eyes without being scattered or 
diffused. This type of reflection is illustrated in Fig. 6'5. 



Figure 65. 

In regular reflection angle A is always equal to angle B. Angle A is 
the “angle of incidence”; angle B the “angle of reflection.” 

Diffuse reflection occurs when light is reflected to the 
eye from a body which has a roughened unpolished surface, 
which by reason of its roughness, scatters or diffuses the 
light rays. The more evenly the light is scattered in all 
directions the more perfect is the diffusion said to be. 

It must not be understood from this, however, that by 
roughness we necessarily mean a surface which appears 
rough to the eye. The roughness we have reference to is 
termed “peaks and depressions,” and these peaks and de¬ 
pressions may be very minute in size. Smooth plaster is a 




MANAGERS AND PROJECTIONISTS 223 

perfect diffusing surface, although it appears smooth to the 
eye and feels smooth to the hand. It is diffusing, however 
because it is not a polished surface, but a surface made up 
entirely of peaks and depressions of sufficient area to break 
up the light. The effect of such surfaces is illustrated in 
Fig. 66. 

“Picture Light” projected upon a screen is reflected from 
its surface back and is scattered in a wide or narrow angle, 
exactly in proportion to the completeness with which the 

surface lacks 
polish and is 
made up of 
peaks and de¬ 
pressions. 

Light rays 
and the ele¬ 
ments of the 
screen surface 
which scatter 
them are both 
of an almost 
infinitely small 
dimension. 

HAZE.— 

Some surfaces 
which have 
been used for 
screens have to 
a certain ex- 
Figure 66. tent both the 

elements of 

polish and of peaks and depressions. Such screens provide 
both regular and diffused reflection, with the result that a 
haze appears before the screen. This haze is the result of 
regular reflection superimposed over or upon the diffused 
reflection. It is a peculiarity of the polished metal surface 
screen, and explains the reason for the failure of many 
homemade metallic projection surfaces. 

VISIBLE ROUGHNESS. —It was for a long while believed 
that screens with surfaces visibly rough had advantage over 
smooth diffusing surfaces, such as plaster hard finish. This 
has been proven to be an error. Always providing the sur¬ 
face be of a character to give a high degree of diffusion 
there is no added advantage in visible roughness. 








224 


HANDBOOK OF PROJECTION FOR 


INTERFERING LIGHT.— One of the very worst faults 
encountered in motion picture theatres, insofar as has to 
do with the screen, is interfering light. By this we mean 
any light other than picture light which strikes the surface 
of the screen. Light interference may be caused by (a) 
stray beams from the projection room which strike the wall 
or ceiling of the auditorium, and are by them reflected to 
the screen. These rays usually come from the condenser. 
Their elimination is a very simple matter, (b). Daylight, which 
is a most prolific cause of poor results at matinee per¬ 
formances. It is nothing short of astounding how little 
attention theatre managers and projectionists pay to the 
thorough excluding of daylight from the auditorium at 
matinee performances. Any daylight which reaches the 
screen, no matter how slight, is highly detrimental to the 
picture. This is such a patent fact that it would seem any 
projectionist or theatre manager would realize and under¬ 
stand it. (c) General auditorium lighting improperly ar¬ 
ranged or improperly shaded. This is another point con¬ 
cerning which many theatre managers display an absolutely 
incomprehensible indifference. We have many, many times 
entered theatres of considerable pretension, which charged 
a top notch admission price, and found the auditorium lights 
literally murdering the picture, or, what is equally bad, found 
unshaded white or brilliant red lights glaring directly into 
the eyes of the audience. Auditorium lighting will be dis¬ 
cussed under the proper heading, therefore we will not go 
into it further here. 

Exhibitors and projectionists should test their screen for 
stray light occasionally. They may only do this best when 
the projector is not working, and the theatre is lighted just 
as it is when the show is on, including the musicians’ lights. 
If under this condition the screen does not look the same all 
over, with absolutely no trace of shadows or bright spots, 
then there is something wrong, and the offending light or 
lights causing the shadows or bright spots should receive 
immediate attention. 

After testing the screen thus, with the entrance doors 
closed, open them and see whether bright spots or shadows 
appear on the screen. This latter test should be made in 
the afternoon as well as in the evening if there is a matinee 
performance. If the opening of the entrance doors affects 
the screen, then the steps necessary to protect the screen 


MANAGERS AND PROJECTIONISTS 225 

from the light entering through the open doors should be 
taken. 

Exhibitors who pay perhaps hundreds of dollars a week 
for film service, and who fail to give proper attention to 
such details as these are doing a very foolish thing. They 
are not getting the best possible results from the film 
service they are buying. They should remember that any¬ 
thing which affects the screen result to its deteriment tends 
to lower box office receipts. Most emphatically a screen 
which is struck by any light other than the picture light 
itself does not give the best possible result. 

Small town theatres whick have windows opening directly 
outdoors may exclude the light effectually by means of 
double, dark colored window shades, the edges of which 
run in grooves not less than one inch deep. These grooves 
may easily be built by a carpenter, and the plan will be 
found quite effectual. One shade will do, but two are 
better, since the single shade is likely to develop pin holes 
which will admit light. 

Standing beside the screen, looking toward the auditorium, 
there should be no unshaded light source visible to the eye 
at any point. If there is, then the light from that source is 
reaching the screen and injuring the result. 

Indirect lighting is a most excellent, form of auditorium 
illumination, provided it be properly installed, but this is by 
no means always done, the most common fault being the 
installation of fixtures too close to the screen end of the 
auditorium. 

Reasonably dark colored, non-reflective wall decorations 
are a great aid in eliminating stray light; also they are very 
restful to the eye, though by this we do not mean to infer 
that the decorations of a theatre should be sufficiently dark 
colored to be gloomy. 

DISTRIBUTION OF REFLECTED LIGHT.— One funda¬ 
mental requirement of a screen surface is that it as nearly as 
possible reflect light equally to all seating space in the 
auditorium, so that the picture appear as brilliantly lighted 
to those patrons seated at a heavy angle to the screen, or to 
those seated in the balcony, as it does to those seated in 
the center of the orchestra floor. If the screen exhibits a 
certain degree of brilliancy to those seated in the center of 
the orchestra floor, and a lesser degree as one moves around 
to one side of the house, it is said to have “fadeaway,” and 
just in proportion as the screen develops this characteristic 


226 


HANDBOOK OF PROJECTION FOR 


it is a poor diffusing surface. If the fadeaway be too pro¬ 
nounced it is not a good surface to employ for a screen, 
except in the case of a very narrow auditorium, no matter 
how convincingly the screen salesman may talk in the en¬ 
deavor to convince you to the contrary. It gives semi¬ 
diffusion of the light, as per Fig. 67. 

SEVEN CLASSES OF SCREENS.— Screen surfaces may 
be divided into seven general classes, viz.: (1) white wall, 
(2) the cloth screen, (3) the kalsomine screen, (4) the 

painted screen, 
(5) the metall- 
ized surface 
screen, (6) the 
glass or mirror 
screen, and (7) 
the translucent 
screen. 

THE WHITE 
WALL. — The 

white plaster 
wall known as 
the “hard fin- 
i s h surface,” 
forms an ex¬ 
cellent surface 
for the projec¬ 
tion of pic¬ 
tures, in that 
it has very ex¬ 
cellent diffusion indeed, while at the same time its power 
of reflection is good for a surface of such high power of 
diffusion. The plaster surface may be cleaned by sand¬ 
papering it lightly, using No. y 2 sand paper, but it can, of 
course, only be cleaned a limited number of times before it 
will be worn down to the brown plaster underneath. 



Semi-diffuse reflection, in which the greater part 
of the light is reflected back in the direction whence 
it came. 


THE CLOTH SCREEN. —This has as excellent powers of 
diffusion as any surface procurable but its power of reflection 
is very low. It is, therefore very difficult to get a brilliant 
picture of a theatrical size on cloth. The cloth screen is 
now seldom used except for strictly temporary installation, 
or by traveling exhibitors. If it is proposed to use cloth a 
good grade of bleached muslin of the kind used for bed 
sheeting is best. It is possible to obtain this cloth 108 inches 
in width. A cloth screen should always be tightly stretched, 












MANAGERS AND PROJECTIONISTS 227 

so that it will present a smooth, unwrinkled, perfectly flat 
surface. 

THE PAINTED SCREEN. —There are certain things with 
relation to paints which have been thoroughly established 
by experiment, but which have not as yet been put into form 
for application in practice insofar as applies to the pro¬ 
jection surface. 

The higher the percentage of pigment contained in a paint 
the higher will be its light-reflecting power. Experiment 
has proven that it is quite possible to produce a paint of 
extraordinary whiteness and very high light reflecting power 
by using heavy bodied oils, cut down by means of volatile 
thinners. It is claimed that by this method flat paints may 
be had which will have from 20 to 25 per cent, higher light 
reflecting power than paints now in general use. 

In ordinary inside house painting it has been- found that 
lead and oil paints deteriorate in light reflecting power by 
about 15 per cent, per year, aside from the loss of reflecting 
power due to accumulations of dirt—due entirely to chemical 
changes in the paint itself. 

It has also been found that kalsomines lose in reflection 
power in about the same ratio, but in this case it is en¬ 
tirely chargeable to absorption of dirt by the porous coat¬ 
ing, hence the loss will be very much higher in a dusty or 
smoky atmosphere. 

WARNING. —Black should never be used to “whiten” 
screen paint, because the addition of the least bit of black 
acts to seriously lower the reflecting power of the coating. 

The foundation for a painted screen surface may be 
tightly stretched cloth, cement finish, plaster, or anything 
else which presents an even, unbroken surface. There are 
a number of screen paints on the market, but up to date 
(subject to foregoing, which forms basis of interesting study) 
we have seen nothing better than either all zinc white, or 
half zinc white and half of a good grade of white lead, 
mixed to a proper consistency with J4 boiled linseed oil and 

\ turpentine, adding just enough ultra-marine or cobalt blue 
to give the paint a very light bluish cast while in the pot. 
When spread on the surface the blue tint will disappear and 
the paint appear dead white. Unfortunately, no authoritative 
data as to its reflective power is available, but it must be 
decidedly superior to that of white plaster, and paint is as 
excellent a diffusing surface as any we know of, excepting 
only plaster and cloth. Colors, of course, may be added to 


228 


HANDBOOK OF PROJECTION FOR 


suit the individual idea, but our own advice is to stick to the 
white paint, without any color of any kind whatsoever. We 
would advise the application of three or four coats of 
tolerably thin paint, rather than a less number of coats of 
heavy paint. The result will be better, and the surface dries 
very quickly. 

The painted screen offers an easily and cheaply renewed 
surface, very excellent diffusion, practically an entire lack 
of fadeaway, and the best possible definition of the picture 
from the front rows of seats. Very many high class theatres 
either already have or now are reverting back to the painted 
screen, because of the advantages above enumerated. Every¬ 
thing considered, it forms one of the most excellent pro¬ 
jection surfaces yet discovered for theatres when the view¬ 
ing angle exceeds 30 degrees, though a given amount of 
light per unit of area will not give as great brilliancy, when 
the screen is viewed from the center of the auditorium, as 
wilUbe had when using either a metallic surface or mirror 
screen. 

There is, however, a great deal of what we will call self 
deception in the matter of screen paints, or rather in the 
methods of painting a screen. When white paint is applied 
directly to a cloth screen a great deal of light “goes 
through.” This light is, of course, lost, and in the endeavor 
to save it some rather weird plans have been evolved. As 
a rule the idea most advanced is that if a coating of semi¬ 
opaque color be applied to the surface, and sufficient coats 
thereof be applied to make it opaque, and then the white 
surface be placed over this opaque surface, or even if the 
opaque coatings be applied to the back of the finished screen, 
no light will “go through,” hence there will be a greater 
brilliancy. The favorite color for the underlying coatings 
has been blue, or a sort of lead color, on the theory that 
the light, striking the blue and being reflected back will 
whiten the overlying surface. 

As to the latter, to an extremely limited extent it might 
possibly be true, but while the opaque coatings underneath 
the white will stop the light from going through, it will not 
and cannot add anything appreciable to the brilliancy of the 
screen. The underlying coat stops the light from going 
through for the very simple reason that it absorbs the rays. 
It does not reflect them back, or anywhere else, modified by 
the fact that if the underlying coat be blue it will absorb 
everything but the blue rays, the question then being can the 


MANAGERS AND PROJECTIONISTS 


229 


blue ray be reflected back through two or three coats of 
white paint, or even appreciably through any minimum 
necessary number of coats. Personally we do not believe 
it is possible this could take place to a sufficient extent to 
have any appreciable effect in whitening the surface, and 
most emphatically it could not add any brilliancy to the 
screen other than what slight effect there might be in 
whitening, which latter effect could be just as well secured 
by adding blue directly to the color. 

FOR AIRDOME SCREENS a paint is necessary. If the 
surface of a theatre screen to be painted be plaster, then it 
should first either be sized with a coating of glue size, or 
painted with a coat of thin shellac. If the airdome screen 
be built of lumber, then we would suggest the installation 
of a painted cloth screen, stretched on a suitable frame, 
over the lumber backing. 

WASHING PAINT SURFACE.— A painted surface may be 
washed, provided it be very carefully done, but the washed 
surface will not have the same brilliancy as a new surface. 

KALSOMINE SURFACE. —A variation of the painted 
screen which we can heartily recommend is the covering of 
either cloth, plaster or cement with one of the patent white 
kalsomines, such as alabastine or muralite, which may be 
had from any dealer in paints, and which may be applied by 
almost anyone after a little practice, though it is, of course, 
always better to have the work done by a competent painter. 
This surface forms a really very excellent screen. In powers 
of diffusion it' ranks very close to white plaster, and while 
we have no authoritative data as to its power of reflecting 
light, it should be as high or even higher than that of white 
plaster. 

CAUTION. —In kalsomiiling one must use a good brush, 
and make no attempt to brush out the work smoothly. 
Instead one should swing the brush in every direction. The 
work must be done fast, because if the edge of the work 
dries so that the next “lap” will not work into the first per¬ 
fectly the joint will show. It is better to have kalsomining 
done by a man experienced in such work. 

Don’t imagine that you can coat a cloth or plaster screen 
with kalsomine or paint and use it indefinitely without doing 
anything more to it. We would very strongly recommend 
that where a plaster or cement kalsomine coated screen is 
used, it be washed off and recoated every ninety days. 


230 


HANDBOOK OF PROJECTION FOR 


It may look clean and bright, but you may be very certain 
it is not. The wall paper or kalsomine on the walls of your 
Home may look perfectly clean, but knead some fresh bread 
into a dough, rub the wall paper with it and see what hap¬ 
pens; perhaps the result will astonish you. Exactly the 
same thing applies to the screen. Kalsomine or paint is 
cheap. Our advice is, USE THEM FREQUENTLY. 

TESTING SCREEN SURFACE.— To test either a kalso- 
mined or painted projection surface place against it a sheet 
of white blotting paper—a desk blotter as to size. If the 
paper appears whiter than the screen, then the screen is not 
in good condition. 

NEAT CEMENT SURFACE.— “Neat” cement is white in 
color. It has been suggested that it would make an ideal 
screen surface. This suggestion may or may not have value. 
We have never seen such a surface, nor have we any data 
concerning the matter. 

GLUE SIZING. —Before undertaking to coat a cloth screen 
with either paint or kalsomine it must be stretched tightly 
on a frame and thoroughly sized with a solution of glue in 
the proportion of from 1 to 2 pounds of glue to the ordinary 
pail of water. The amount used will depend upon the grade 
of glue. 

METALLIZED SCREEN SURFACES.— Screen surfaces 
to which various compounds containing more or less pow¬ 
dered aluminum or other powdered metallic substances 
have been applied, have been and still are quite popular, 
though the tendency is to revert back to the plain white 
painted or kalsomine screen, except in theatres having a 
rather narrow auditorium. 

Metallic surface screens have for their base some kind of 
cloth fabric, to which the metallic substances are applied by 
processes which are held jealously secret by the manu¬ 
facturers. Their sole advantage lies in the fact that within 
certain angles the projectionist is able to get a very high 
degree of brilliancy per unit of area at considerably less 
expenditure of light, hence of electric energy, than is possible 
with a more perfect diffusing surface. This relatively high 
brilliancy, however, usually only extends over an angle of 
20 to 30 degrees, outside of which angle there is a decided 
fadeaway. See tables 12 to 16 inclusive. There is also a 
more or less pronounced tendency to discoloration of the 
surface, especially in damp, climates, though this latter fault 


MANAGERS AND PROJECTIONISTS 


231 


need not worry the purchaser if he secures a proper written 
guarantee against such fault. 

There is a very decided difference in metallic screen sur¬ 
faces, but the characteristic of the different types may be 
examined in tables 12 to 16, so that the purchaser may know 
precisely what effect he will get from any given type of 
screen. 

WARNING.—It is a very difficult matter to apply metals 
(either in powder or paint form) to a screen surface in such 
way as to secure the best possible light diffusion, and the 
exhibitor who prefers to use a metallic surface screen should 
by all means purchase the screen from a reliable manu¬ 
facturer. The manufacturer makes a specialty of preparing 
such surfaces; also he usually applies stretching devices 
which will allow of the screen being properly installed. It 
is almost impossible, and certainly is entirely impractical for 
the projectionist or exhibitor to make a satisfactory home 
made metallic surface screen. 

CHALK SURFACE.— There is possibility for an excellent 
projection surface in common chalk. This surface has to 
some extend been used, and has given excellent results. The 
surface is made by rubbing ordinary white chalk, such as 
carpenters use for their chalk lines, and which may be had 
cheaply at any hardware store, on plaster or any other 
suitable surface. Even school crayons, broken in two and 
used flatwise, will do. Such a surface costs very little in 
money, but requires considerable labor to get it on evenly. 
The picture stands out on a chalk surface with surprising 
brilliancy. 

Rubbed on a plaster wall a chalk surface may be removed 
for renewal by means of an ordinary school blackboard 
eraser, and may be renewed by a few cents’ worth of chalk, 
plus considerable labor. 

MIRROR SCREENS —The mirror screen consists of a 
sheet of plate glass, the back of which is coated precisely the 
same as is an ordinary plate glass mirror. Its face is then 
sand-blasted to a dull finish, which may be made rough or 
smooth, according to the condition under which the screen 
is to work. The light is caught on the ground face and a 
portion of it is reflected back. The rest of it goes through, 
strikes the silver at the rear surface and is reflected back to 
the rough finish. This has the effect of producing a very 
high efficiency and a very brilliant result when the screen is 
viewed from in front; but due, we believe, in some measure 


232 


HANDBOOK OF PROJECTION FOR 


to the thickness of the glass, there is tendency to out of 
focus when a mirror screen is viewed at a wide angle. The 
satin finish mirror screen is an ideal installation for the 
long, narrow theatre, by reason of the fact that the audience 
will all be seated practically directly in front of it, under 
which condition a very brilliant picture may be had with a 
comparatively low projection light value; also the satin 
finish mirror screen has the peculiarity that the further you 
get away from it, within reason, of course, the more brilliant 
the picture appears. It is, therefore, particularly of value in a 
very deep, narrow house. 

One of the principal objections to the mirror screen is that 
it is costly, difficult to install and subject to some, though 
slight, risk in the item of breakage. Once installed, however, 
barring very improbable accidental breakage, it should re¬ 
quire no attention, except on occasional washing, for many 
years. 

TRANSLUCENT SCREEN. —The translucent screen is 
either made of translucent material, such as tracing linen, or 
it is of ground glass. With this type of screen the pro¬ 
jector may be located on the side of the screen opposite 
from the audience, which will view the picture through the 
screen. The image appears on both sides of the screen, but 
is reversed to the projectionist, to whom all titles and other 
reading matter will read backward. 

When projecting through a translucent screen (called “rear 
projection”) the film is placed in the projector with the 
emulsion side toward the screen, instead of toward the light 
as in ordinary projection. 

It is possible to use ordinary cheese cloth or thin muslin 
cloth for a translucent screen, but if this be done the pro¬ 
jection lens must be sufficiently below the center of the 
screen so that a straight line from the eye of the spectator 
to the lens will not pass through any part of the picture. In 
practice this means that such a screen cannot be used for 
rear projection at all if there is a balcony in the theatre. 
The reason for this is that any spectator who sits in such 
position that the eyes will be in line with any portion of the 
picture and the lens will see the brilliant lens spot through 
the screen. The ground glass, tracing linen and screens of 
similar characteristics break up this bright spot and render it 
invisible. 

If a cloth screen be used the result will be greatly im¬ 
proved if it is kept wet with water. 


MANAGERS AND PROJECTIONIST^ 


233 


The best screen of all for rear projection is ground glass, 
because it causes but a comparatively slight loss of light; 
also it gives very good diffusion, though it is claimed there 
is advantage in grinding the surface coarse for a wide house 
and fine for a narrow house. 

Tracing linen makes a fairly satisfactory translucent 
screen, its worst feature being that it cannot be had suffi¬ 
ciently wide, hence the screen must contain a seam which 
cannot be made invisible by any present known process, and 
will show more or less in the picture. 

Rear projection is, however, but very little used. It pre¬ 
sents advantages where conditions are such that it can be 
properly employed, but in 9 cases out of 10 where it is at¬ 
tempted the distance of projection is so short that really 
good results cannot possibly be had. In fact rear projection 
usually is employed as more or less of a makeshift. 

Where it is possible to obtain a distance from projector 
to screen which will admit of the use of a projection lens 
of not less than 4 inches E. F., however, rear projection on 
a glass or other high class translucent screen comes pretty 
near being ideal, since the projection room with its noise, 
heat and fire risk may be located entirely away from the 
audience, presumably outside the theatre. 

The question is often asked, can we locate a translucent 
screen at the proscenium line, set the projector at the rear 
of the stage and get a good picture? The answer is an em¬ 
phatic no! It is never advisable to attempt the projection of 
a picture of a size suitable for theatre work with less than 
50 feet from the lens to screen, and 40 feet may be con¬ 
sidered as an absolute minimum, understanding, however, 
that real high class results cannot be had at 40 feet unless 
the picture be smaller than is ordinarily suitable for the¬ 
atrical work. Another very serious objection to this plan is 
that it places the screen altogether too close to the front row 
of seats. 

THE CONCAVE SCREEN.— There is no advantage in the 
installation of a concave screen surface, except possibly in 
cases where the distance of projection is such that a very 
short focal length projection lens must be employed—say a 
lens of less than 3.5 inch E. F. Under such a condition there 
may be some advantage in a concave screen surface, but 
given a normal projection condition any advantage such a 
surface might offer would, in our opinion, be more than offset 
by disadvantages it would present in other directions. In 


234 


HANDBOOK OF PROJECTION FOR 


our opinion where the condition is such that a projection 
lens of 4.5 inch E. F. or more is required a concave screen 
presents no advantage whatsoever. It is one of those things 
which looks very plausible, but which will not stand the cold 
light of critical analysis. 

HEIGHT ABOVE THE FLOOR.— The height of the screen 

above the floor must, of course, to some extent, be governed 
by conditions obtaining in the individual theatre. Where 
there is a stage we believe the general effect will be best if 
the bottom of the picture be located quite close to the floor. 
Other things being equal, this we believe, gives the most 
nearly lifelike effect to the picture. 

There is, of course, a distinct advantage in locating the 
picture high up on the wall. In some countries this is the 
almost universal practice, the auditorium floor being left 
perfectly level. Such location, however, also has very serious 
disadvantages, the principal one of which is the tendency to 
emphasize in the mind the fact that one is looking at a 
picture, and not a real performance; this because of the 
fact that in the home and elsewhere we see the picture hung 
on the wall, and the mind, to some extent, subconsciously 
connects the moving picture which is located high up above 
the floor with the picture on the wall. 

Everything considered we believe that, where it is practi¬ 
cal, the best general effect will be had by locating the bot¬ 
tom of the picture about 6 feet above the auditorium floor 
where the screen is on a wall, and no orchestra is used. If 
there be an orchestra, then it will be better to add perhaps 2 
feet to the above, in order to, as far as possible, avoid the 
effect of the musicians’ lights. 

EYE STRAIN.— Many people avoid the photoplay theatre 
either because they have seen motion pictures under cir¬ 
cumstances which set up eye strain, or because they fear the 
motion picture will cause injury to their eyes. Eye strain in 
moving picture theatres may be attributed to five main causes, 
viz.: flicker, poor definition, poor illumination, a too large 
picture, and glare spots. 

FLICKER. —It is a fact well understood by most people 
that the pupil of the eye expands and contracts in direct 
proportion to light intensity. The retina of the eye is most 
comfortable and “sees” best at certain given light intensities, 
which vary considerably with the individual. The office of 
certain muscles known as the “muscles of accommodation” 
are to expand or contract the pupil of the eye to let in just 


MANAGERS AND PROJECTIONISTS 235 

sufficient light to maintain the value most comfortable to 
the retina. 

When flicker occurs the tendency of the muscles of accom¬ 
modation is to open the pupil during the period of darkness 
to a point where a greater proportion of light enters when 
the picture is being projected than is “comfortable” to the 
retina. This causes a distinct shock to the retina. Another 
effect is a tendency of the muscles of accommodation to 
follow the rapid alternations of light and darkness, and this 
sets up a terrific strain indeed. 

In this connection let it be clearly understood that when 
flicker occurs it occurs because of some wrong procedure 
somewhere in the process of projection. Flicker can always 
be eliminated by the projectionist if he understands his busi¬ 
ness, is provided with proper equipment and is unhampered 
by orders from the management which prevent him from 
applying the remedy. 

The screen itself never produces flicker, but where a screen 
of comparatively low efficiency is used, and is later replaced 
by one of the same area, but of higher efficiency, if the same 
amperage be used the tendency to flicker will be increased by 
the added brilliancy of the reflected light. 

The period of darkness remains of the same duration as to 
time, but the light is more brilliant, hence there is added con¬ 
trast. If the light were reduced until the picture on the new 
screen had no greater brilliancy than the picture on the old 
screen, which may be done by reducing the amperage, it 
would be found that the flicker will be neither more nor less 
than it was before. 

Flicker due to the alternate opening and closing of the lens 
by the revolving shutter of the projector is utterly inex¬ 
cusable. When it occurs, either the projectionist lacks the 
knowledge necessary to eliminate it; lacks energy to do the 
necessary things to eliminate it, or the speed of projection is 
too slow. 

LACK OF DEFINITION AND EYE STRAIN.— Lack of 
sharp definition in the picture operates to set up heavy eye 
strain. If you doubt this, have a stenographer do some type¬ 
writing, making about four carbon copies on ordinary paper. 
The last copy will be “fuzzy.” Try to read a page or two of 
that kind of copy and see what happens to your eyes. The 
writing is out of “focus,” very much the same as is a picture 
<on the screen when it lacks definition. 

Lack of definition may be due to several things. A poor 


236 


HANDBOOK OF PROJECTION FOR 


lens may cause it. A wrongly adjusted optical system may 
cause it. Oily film may cause it, or the cause may be in¬ 
herent in the film itself. 

In view of the foregoing, and the importance of prevent¬ 
ing eye strain in motion pictures now that they have become 
such an enormously popular form of amusement, the theatre 
management should expend some energy and money in 
securing the best possible lenses, the projectionist should 
thoroughly understand the handling of the optical system of 
his projectors, and the projectionist who is careless and 
“sloppy” enough in his work to get oil on the film should be 
promptly discharged. For a manufacturer to send out film 
which cannot be projected in sharp definition on the screen 
is little short of criminal, the crime being against the eye¬ 
sight of this and future generations. 

EYE STRAIN AND POOR ILLUMINATION.— In propor¬ 
tion as an audience becomes deeply interested in the picture 
story, it will make every effort to catch every phase of the 
projected picture. It will closely watch every detail of the 
action, both major and minor, since it sometimes happens 
that upon some slight change of expression, a side glance or 
the wink of an actor’s eye, or some comparatively slight 
detail in the action, will hinge very important details of the 
story itself. The audience, therefore, is anxious to miss 
nothing, and if the illumination of the picture be not suffi¬ 
cient, it is entirely understandable that comparatively heavy 
eye strain may be set up. 

We read the picture story upon the screen almost exactly 
as we read the printed page of a book. If we attempt to 
read a book with a poor light, or when it is shaking or mov¬ 
ing (jumpy picture) the result is a strain upon the eyes, 
which may be entirely avoided by improving the illumination 
and holding the book still. This is just plain common sense. 
It is a point which even the most obtuse can readily under¬ 
stand. 

Precisely the same thing applies in projection. We im¬ 
prove the illumination by projecting more light to the screen 
through the film, and instead of “holding the book still,’ we 
prevent the picture from “jumping” on the screen. 

EYE STRAIN AND SIZE OF SCREEN.— The size of the 
screen plays a highly important part in the matter of eye 
strain. If the screen be too large, or, what amounts to the 
same thing, if the front rows of seats be too close to the 
screen, very heavy eye strain will be set up for those occupy- 


MANAGERS AND PROJECTIONISTS 


237 


ing the front rows of seats. This is for a double reason. In 
the first place, due to the excessive size of the screen or the 
nearness of the seats to it, the eye must travel over a wide 
surface in following the action. It requires no great wisdom 
to understand that this in itself is very hard on the eyes. 
Then, too, if the screen be too large, or if the front rows of 
seats be too close to it, the tendency to eye strain is aug¬ 
mented, because the picture will not be seen in sharp focus 
from these seats. 

GLARE SPOTS. —One of the most prolific sources of eye 
strain is what is known as “glare spots,” which means a rela¬ 
tively small spot which is highly illuminated as compared to 
its surroundings, and which falls within range of the eye of 
the theatre patron who is looking at the screen. 



In their pamphlet, “The Motion Picture Theatre, Its Illum¬ 
ination and the Selection of a Screen” (which we commend to 
the projectionist for addition to his library), the Eastman 
Kodak Company says: 

“No area of the interior of the theatre visible from any seat 
in the audience, except the picture itself, should have an 
apparent brightness of more than 2.5 to 3.0 foot-candles. This 
applies to the walls near a lamp, to the lamp itself if it is not 








238 


HANDBOOK OF PROJECTION FOR 


concealed, to any diffusing globes or fixtures used, and in 
general to any part of the interior of the theatre. For exam¬ 
ple, a sheet of white paper illuminated by a 25 watt lamp at 
at distance of one foot, has an apparent brightness of about 
20 foot-candles. A sheet of music illuminated in this way, 
if visible from the audience, becomes a glare spot and may 
cause great discomfort. Arrangements should therefore be 
made which, while providing adequate illumination for the 
musicians, will prevent the illuminated sheets from being visi¬ 
ble to the audience. Lights under a balcony are particularly 
bad and should be used only with a properly designed indirect 
lighting system. Considerable attention should be paid to 
the character and position of exit signs. While it is neces¬ 
sary to make such.signs very conspicuous, this can be accom¬ 
plished without making them so brilliant as to become dis¬ 
agreeable glare spots.” 

We agree with every word of the foregoing. Glare spots 
caused by side lights, clocks, wrongly-made exit signs, lights 
on the ceilings of balconies, and music lights, are nothing else 
than a crime against the eyesight of this and future genera¬ 
tions. They are the product of carelessness or ignorance, or 
both. They have no legitimate excuse under heaven. 

In Fig. 67j4, A is the eye of a spectator looking at a screen, 
with four more or less concentrated points of light glaring 
into his eyes, viz.: two “side lights,” a clock light and an exit 
sign located beside the screen and unintelligently illuminated. 

If it is desired that a clock be located on the theatre front 
wall its face may be illuminated acceptably, and absolutely 
without glare, as follows: 

From a photographer secure a sheet of dull black paper, 
such as comes wrapped around photographic plates. Cut 
it circular and the size of the clock face. Have a painter 
paint numerals (Roman) from one to twelve, in their proper 
place. Cut a half-inch-diameter hole in the center for the 
clock hand post. Split the paper from outside to center hole 
between any two figures, which enables you to slip the black 
face under the clock hands without disturbing them, where¬ 
upon it may be attached to the clock face, with numerals in 
correct position, by means of a few spots of Le Page’s glue, 
without in any way injuring the white clock face, because 
upon removal of the black face the glue may be moistened 
and washed off. 

Now paint the hands dead white, or affix to them false 
hands made of lightweight white cardboard, which may be 


MANAGERS AND PROJECTIONISTS 


239 


done by means of a white thread. Make the paper hands con¬ 
siderably wider than the original hands. 

Now suspend an incandescent lamp in a can, or suitable box, 
and in one side cut a hole just barely large enough to let 
out a circle of light of sufficient diameter to illuminate the 
clock face, AND NOTHING ELSE. Or, better still, affix in 
a hole in the side a small lens which will project a circle 
of light covering the clock face AND NOTHING ELSE. 

The audience can read the time from white hands on a black 
face very much more readily than from black hands and a , 
white face, and your glare spot will have been entirely elim¬ 
inated. 

EXIT LIGHTS can be made conspicuous, and at the same 
time absolutely non-glaring, as follows: Paint the letters 
EXIT in red letters of suitable height, and outline them in 
black, so that only the letters show—which is exactly what 
is wanted. No official with a grain of sense or an atom of 
knowledge concerning theatre lighting can or will object to 
this, provided you do it intelligently. The capable official will 
commend the plan. 

You may make your present black-letter-on-light-red- 
ground glaring exit signs both efficient and harmless by shov¬ 
ing in a sheet of DARK RED glass between the light and the 
letters, or two sheets of light red glass if the dark red cannot 
be had. It will cost you a few cents, yes, but will add im¬ 
measurably to the comfort of the eyes of your audiences. 

CAUTION.—Don’t imagine that because no one complains, 
your glare spots are unobjectionable. The theatre patron 
does not blame the right thing when his or her eyes hurt. 
He does n<ot know or realize the seat of the trouble, and., 
blames it on “the pictures.” But the point is that he or she 
stays away from picture theatres because “the pictures hurt 
my eyes,” or else go to another theatre where “the pictures 
don’t hurt my eyes” because the man there is on to his job 
and does not tolerate glare spots. 

WARNING.— Do NOT use an exit sign with black letters 
on a glass painted red. The paint may be O. K. at first but 
soon begins to scale off, and a glare spot is thus gradually 
set up before you realize it. USE RED GLASS ONLY. It 
may be had of or obtained for you by any dealer in photo¬ 
graphic supplies. 

FLAT SURFACES—LOCATION —Whatever the surface 
of the screen be composed of, it is plain that it should be as 


240 


HANDBOOK OF PROJECTION FOR 


nearly as possible perfectly flat, without wrinkles, bumps or 
uneven places, and that its color and “brilliancy” should be 
precisely the same for every portion of its surface. The 
screen should always set as nearly as possible with its center 
level with, and in line sidewise with the projector lens. This 
latter condition is practically never possible of accomplish¬ 
ment where two projectors are used, since one or the other 
or both must necessarily set slightly to one side of the cen¬ 
ter of the screen. 

OUTLINING THE PICTURE. —No matter what type of 
screen is used, the picture should invariably be outlined in 
some very dark non-gloss color. This outline should be at 
least 2 feet wide, top, bottom and sides, and 3 or 4 feet is 
better. The outline should extend slightly into the picture. 
In other words the picture should overlap slightly on the 
outline, say one or 2 inches' all around. 

The reason for this latter recommendation is that it serves 
to greatly minimize the effect of any movement of the pic- 



Figure €8. 






MANAGERS AND PROJECTIONISTS 241 

ture as a whole on the screen; also it serves to conceal any 
vibration there may be in the projector aperture itself. 

The effect of the outline is to secure added contrast for 
the picture. A picture projected to the center of a white 
screen without an outline has not anything like the sharp, 
pleasing contrast which the same picture has when projected 
to a white screen properly outlined by a dark border, or a 
border of dead (non-gloss) black. 

In Fig. 68 we see a characteristic moving picture theatre 
screen setting, with the screen outlined in black. In former 
books we have invariably recommended non-gloss black for 
the picture outline, but while this is ideal in some ways, it 
frequently happens that black will not harmonize with the 
other screen surroundings. In view of this fact, this par¬ 
ticular recommendation is modified to the extent that any 
reasonably dark non-gloss color will serve fairly well as a 
picture outline. 

The Eastman Kodak Company laboratories have made cer¬ 
tain rather exhaustive experiments, seeking to determine the 
best methods to pursue in the matter of screen surroundings 
and picture outline border. Concerning the latter they say: 

“Some observations were made during the course of the 
experiments which will probably upset some existing con¬ 
ventions and increased the comfort of the motion picture 
patrons. For instance, the black velvet frame which fre¬ 
quently surrounds the screen is found undesirable and a 
neutral gray is suggested in its place. The reason is simple. 
Suppose the illumination of the strongest highlight of the pic¬ 
ture is 10 foot candles. Under these conditions the brightness 
of the black velvet frame would be found to be about 0.001 
foot-candles. This makes the ratio of the two or the bright¬ 
ness contrast equal to 1 to 10,000. This contrast is beyond the 
power of the eye to record and results again in overtaxing the 
process of adaptation. By using a material with a higher 
reflecting power than black velvet, the contrast between the 
screen and the frame may be brought within the range of the 
eye. If the brightness of the frame is raised to 0.02 foot- 
candles, the contrast between the strongest highlight in the 
picture and the frame is 1 to 500. Scientists say that this is 
about the limit of contrast which the eye can endure with 
comfort. In general, therefore, the black velvet frame should 
not be used but, in its place, a material which has a reflecting 
power sufficient to raise the apparent brightness of the frame 
to something like 0.02 foot-candles. 


242 


HANDBOOK OF PROJECTION FOR 


“The selection of the material will depend upon a number 
of factors: the illumination of the theatre and the distance 
of the screen behind the front of the stage being the prin¬ 
cipal ones. For experimental purposes in the laboratory it 
was found that covering the black frame with white mill net 
was quite satisfactory. Such an expedient will not in general 
be found satisfactory in practice since this material will 
undoubtedly fail to harmonize with the elegance and richness 
of finish frequently found in the modern motion picture 
theatre. In many cases the screen area is surrounded by 
drapings of silk, velvet, or other fabrics and in such cases it 
is suggested that a fabric harmonizing with the general 
decorative scheme be used as a draping immediately around 
the screen area, the color that will give a satisfactory result 
being such as in ordinary terminology is referred to as a 
rather dark gray. A very pleasing result was obtained in an 
experimental installation by the use of a screen frame covered 
with a warm-gray burlap such as is used for wall coverings. 
In case the decorative scheme is carried out not by the use 
of fabrics but by the use of painted surfaces, the frame 
should be made by use of a rather dark gray paint. Of 
course, it should be understood that in case a true gray does 
not harmonize well with the decorative scheme of the interior 
some rather dark color tone (including colors usually referred 
to as warm or cool grays) may be used with advantage. In 
any event, small samples of fabric or small panels painted 
with various colors should be tried by placing them tem¬ 
porarily in position near the screen and the final choice made 
when a material or paint is found having a reflecting power 
such as to make the frame appear of the correct brightness.” 

We are unable to altogether agree with this. We see no 
reason why the screen border should be visible to the eye 
at all. In fact, the less visible it is, it seems to us the better 
is the condition. However, we yield all due respect to the 
views of the gentlemen who made these experiments and 
pass the matter along to you for consideration, with the note 
that we still adhere to our recommendation of either a dead 
black, or at least a very dark non-gloss screen border. 

We commend the booklet issued by the Eastman Kodak 
Company, entitled “The Motion Picture Theatre, Its Illum¬ 
ination and the Selection of the Screen.” 

It is a twenty-four-page, paper-covered phamplet. It will 
be sent gratis to projectionists who say in what theatre they 
are employed. Get it for your library. 


MANAGERS AND PROJECTIONISTS 


243 


NON-GLOSS SCREEN SURROUNDINGS.— As to the im¬ 
mediate screen surroundings, it is highly important that they 
be absolutely non-gloss in character, and not too light in 
color. This is of very great importance indeed where an 
orchestra of considerable size is located immediately in 
front of, or near the screen. Very great injury is often done 
to the screen result by the light reflected by the white sheet 
music to the light colored semi-gloss screen surroundings, 
and by them re-reflected back to the screen. Where there 
are from 20 to 40 orchestra lights it requires no great wisdom 
to understand that a vast amount of reflected light may reach 
the screen in this way, all of which not only adds extraneous 
light to the lighted portions of the picture, but also to the 
shaded and black portions, causing the latter to appear a 
dirty gray color, instead of pure black. The direct effect of 
this is to very greatly injure the contrast of the picture. 

PAINT STAGE FLOOR.— Where a screen is set well back 
on the stage of a theatre having a balcony, it is highly im¬ 
portant that the floor of the stage be either covered with 
non-gloss black cloth or painted non-gloss black. Unless 
this is done the light reflected from the floor will be very 
annoying to the eyes of the patrons seated in the balcony or 
at least it will detract from the contrast and beauty of the 
picture. 

SIZE OF PICTURE.—(Also see “Definition and Magnifica¬ 
tion,” Page 245.) —The size of the picture has been the sub¬ 
ject of perhaps more argument than any other one thing in 
connection with the motion picture theatre auditorium. This is 
because of the fact that a number of things are directly in¬ 
volved in the matter. The author of this work has always 
opposed large pictures. He has repeatedly said, and does 
still say, he has never yet seen a theatre in which he con¬ 
sidered there was any real necessity for a picture of greater 
width than 18 feet, and those theatres which really require a 
picture wider than 16 feet are very rare indeed. 

The author has stood in Madison Square Garden, New 
York City, at a distance of more than 200 feet from a 16-foot 
picture and has been able to read both the titles and sub¬ 
titles with very little effort. He was able to follow all the 
action of the photoplay without the slightest difficulty. 

Mazda projection has served to demonstrate the fact that 
what was formerly believed to’be an impossibly small picture 
is really plenty large enough for the ordinary theatre. We 


244 


HANDBOOK OF PROJECTION FOR 


have watched the projection of a 12-foot picture in a theatre 
seating 1,500, with the audience apparently thoroughly 
satisfied. 

We will now endeavor to discuss this matter of picture size 
in some of its more important details. In the first place the 
size of the picture has directly to do with the value of the 
front rows of seats, because if the picture be too large in 
proportion to its distance from the front row of seats, then 
those occupying the front seats will be subject to heavy eye 
strain, besides having a highly unsatisfactory view of the 
picture. The value of these seats will therefore be greatly 
reduced. The eye strain will be caused by two separate 
things, viz.: first, the picture will not appear in sharp focus, 
which in itself causes heavy eye strain; second, if the person 
be seated too close to a picture of large size the movement 
of the eye in following the action on the screen through the 
wide angle involved will set up terrific strain. 

After a great deal of study, observation and consideration 
we have concluded that the front row of seats should never 
be closer than 20 feet from a 16-foot picture, and in order 
that the same angle of view be maintained it is necessary 
that one foot 3 inches of additional distance be added for 
each additional foot of picture width. 

In exact opposition to the foregoing it must be remem¬ 
bered that if the picture be too small and the auditorium be 
a long one, then eye strain may be set up for those who 
occupy the rear seats, though this ordinarily only holds good 
where the rear seats are an unusually great distance from 
the screen. 

We think we may safely say that there will be no appreci¬ 
able eye strain for those of normal eyesight if no seats be a 
greater distance than 100 feet from a 16-foot picture. As a 
matter of fact a great many people would experience no eye 
strain at a considerably greater distance, but we believe 100 
feet may be accepted as a fairly safe guide for the average 
eye. Those who experience eye strain at that distance can of 
course secure seats nearer the screen and we must remember 
that the smaller the picture the more brilliant it can be made, 
hence the greater distance it may be viewed without eyestrain. 

The smaller the picture, within reasonable limits of course, 
the more valuable the front rows of seats become. 

Except under very unusual circumstances we strongly 
recommend that no picture exceed a maximum width of 18 
feet. As to the minimum, it may be fairly said that a 10-foot- 


MANAGERS AND PROJECTIONISTS 


245 


wide picture is about as small as any one would care to use 
for theatrical purposes. 

DEFINITION AND MAGNIFICATION.— Increase in pic¬ 
ture size is only had by increasing the magnification of the 
film photograph in its image at the screen, with the natural 
result that definition is impared, it very seldom being per¬ 
fectly sharp in the photograph itself to begin with. See 
magnification of defects, page 246. 

PICTURE SIZE AND LIGHT DEMAND.— It must be re¬ 
membered that as the size of the picture is increased the 
amount of light necessary to maintain its brilliancy per unit 
of area increases rapidly. 

The magnification of the film photograph is in any event 
enormous. Its linear magnification may be found by multi¬ 
plying the width of the image in inches by 32 and dividing 
that result by 29. The result will be the number of times 
the film photograph is magnified in the width of the screen 
image, the projector aperture being 29/32 of an inch wide. 
The following figures are interesting. 

Table No. 9. 

Size of Picture. Surface Area. Magnification. 

9x12 108 Square feet 158.88 diameters 

12x16 192 Square feet 211.84 diameters 

15x20 300 Square feet 264.80 diameters 

If you were to cover a 16-foot picture with film photo¬ 
graphs just the size of the projector aperture it would re¬ 
quire 44,944 of them to do it. And since there are 16 photo¬ 
graphs to the foot of film it would be necessary that 2,788 
feet of film be cut up to supply the photographs. 

Table number ten gives the height and area in square 
feet of pictures from 10 to 20 feet wide, by one foot steps. It 
also gives the percentage of illumination or brilliancy per 
unit of area each size would have as compared with the 10- 
foot-wide picture, amount of light passing the revolving 
shutter of the projector being the same in all cases. 

Table No. 10 is enlightening. We find that by increasing 
picture size from 10 feet to 14 feet we have decreased its bril¬ 
liancy by 49 per cent., and that a 16-foot picture will require 
61 per cent, additional light to be as brilliant as the 10-footer. 

Of course the table assumes that the same percentage of 
the total light reaches the screen in every case. For prac¬ 
tical purposes the percentage column really shows the per¬ 
centage of area in reverse. For instance: the 10-foot picture 


246 


HANDBOOK OF PROJECTION FOR 


has just 25 per cent, of the area of the 20-footer; the 10-foot 
picture has just 39 per cent, of the area of the 16-footer, and 
'so on. 

Table No. 10. 


Width in Height in 


Feet. 


Feet. 

Area Sq. Ft. 

Brilliancy. 

7.50 

X 

10 

75. 

100 

per cent. 

8.25 

X 

11 

90.75 

82 

ii 

9. 

X 

12 

108.00 

69 

ii 

9.75 

X 

13 

126.75 

59 

a 

10.50 

X 

14 

147. 

51 

a 

11.25 

X 

15 

168. 

44 

a 

12. 

X 

16 

192. 

39 

a 

12.75 

X 

17 

216.75 

34 

ii 

13.50 

X 

18 

243. 

29 

a 

14.25 

X 

19 

270.75 

27 

ii 

15. 

X 

20 

300. 

25 

ii 


MAGNIFICATION OF DEFECTS.— One phase of picture 

magnification, or picture size, should not be overlooked, 
especially by the exhibitor showing old films, viz.: the effect 
of magnification on defects. As has been shown, the magnifi¬ 
cation of the original photograph in any picture of theatrical 
size is terrific. But in the larger sizes it is, of course, very 
much greater than in the smaller. 

Applied to defects, suppose you have film which has a good 
deal of “rain.” If the actual scratch in the film itself be 
.015625 (1/64) of an inch wide it will appear as a mark ap¬ 
proximately 2.5 inches wide in a 12-foot picture, but in a 20- 
footer it will be widened to a little more than 4 inches. We 
thus see that as the picture width is increased all defects in 
the film photograph are magnified and made more visible, but 
especially this applies to rain, it being more or less continu¬ 
ous throughout old film. 

It may also be noted, in passing, that any side motion of 
the film in the aperture will be magnified on the screen in 
the same proportion. If the film moves sidewise .015625 
(1/64) of an inch in the aperture, the 12-foot picture on the 
screen moves about 2.5 inches and the 20-footer moves a little 
more than 4 inches. 

TINTED SCREEN SURFACE. —Many experiments have 
been made with intent to soften or improve light tone by 
means of tinting the screen surface. We have never been 
enthusiastic about the scheme. We believe that the glaring 
whiteness of the light from a high amperage arc may well be 




MANAGERS AND PROJECTIONISTS 


247 


softened, but this should be done either by chemicalization of 
the carbons or by the employment of lenses made of glass 
which will accomplish the purpose. 

That the former is possible has apparently been amply 
proven by the work accomplished in the controlling of the 
tone of the light emanating from alternating current carbons 
by means of chemicalization of the carbons themselves. 
That the latter is possible, without serious light loss, has 
been proven by the “amberlux” lens which was for a con¬ 
siderable period of time marketed by H. Dashler Warner, of 
Columbus, Ohio. This latter was nothing more than a piano 
surface glass, which slipped into the jacket of the projection 
lens at the screen end of same. It had the effect of mellow¬ 
ing the light tone by removing the chalky glare, and seemed 
to do it without serious loss of screen brilliancy. 

To sum up, we are firmly convinced that the screen surface 
should, except in very narrow auditoriums, be as nearly as 
possible a perfect diffusing surface, that it should present a 
perfectly flat surface, and that the surface should be as white 
as it is possible to get it, the possible resultant chalkiness of 
the whites being eliminated by one of the means suggested. 

LOCATING THE SCREEN AT THE FRONT OF THE 
HOUSE. —Experience has amply proven that the location of 
the screen at the end of the auditorium where the audience 
enters, with the projection room at the opposite, or rear end 
of the auditorium, is very bad practice indeed. Its effect is 
not good in any way, and when we consider the fact that the 
modern projection room is absolutely fireproof, and that if 
the port shutters be properly constructed and fused, and the 
projection room be properly ventilated, no evidence of any 
fire which may occur therein will be visible in the auditorium, 
we readily see that absolutely no element of safety is served 
by a front of the house screen location. Local authorities 
will do well to pay more attention to the proper construction 
of the projection room, the proper construction of its port 
fire shutters, the proper location of the fuses controlling the 
port fire shutters, and the proper ventilation of the projec¬ 
tion room, instead of evolving such utterly useless, not to 
say foolish schemes as placing the screen at the entrance 
end of the auditorium. 

LOCATION OF SCREEN ON STAGE.— Where the screen 
is located on a stage, and the theatre is used for motion 
pictures only, the screen should in any event be located far 
enough back so that there will be a minimum distance of 20 


248 


HANDBOOK OF PROJECTION FOR 


feet between the front row of seats and the screen, if the 
picture be 16 feet or less in width. See Page 244. For each 

added foot of picture width there should be an additional one 
foot and three inches between the front row of seats and the 
screen in order to maintain the same viewing angle from the 
front seats. 

If the depth of the house from the proscenium to the rear 
row of seats be not to exceed 75 feet, it is always very much 
better to set the screen back on the stage as far as it can be 
placed without interfering with the view of the screen from 
the extreme front side seats. Those in the rear seats will 
still be close enough to have a good view of the screen, 
while those in the front rows and at the side of the audi¬ 
torium will have a vastly improved view over what it would 
be if the screen were further front. 

COMBINED VAUDEVILLE AND PICTURES.— Many 

theatres use a mixed performance of vaudeville and feature 
pictures. Where this is done it is very much better that the 
pictures follow the vaudeville, because the screen may then 
be placed at the rear of the stage, where those occupying the 
front rows of seats will have at least a fairly good view with¬ 
out serious eye strain. If the pictures precede the vaudeville, 
then it will usually be necessary to place the screen near the 
front curtain, in what is known in theatrical parlance as 
“one,” in order that the stage may be set for the first vaude¬ 
ville act while the picture is running. This sets up a very 
bad condition for patrons occupying the front rows of seats. 
They will experience heavy eye strain by reason of the fact 
that the picture will not appear to them in sharp focus, and 
for other reasons set forth on page 244. 

In theatres using a combined vaudeville-picture bill there 
is, except in a comparatively few isolated cases, an astound¬ 
ing indifference shown to the proper presentation of the 
picture, although the picture in many cases supplies fully 
half the bill. The screen more often than not is badly 
located, and very often is to all intents and purposes merely 
a flat sheet of very poorly coated muslin. 

In such houses the screen should be stretched on a sub¬ 
stantial frame, and should slide up and down in grooves. 
The screen should be properly counter-weighted, as can be 
very easily done in modern theatres. Where this plan is 
used the screen will always be precisely in the same place, 
and currents of air will not move its surface. 

We have often sat in a high-class vaudeville-picture thea- 


MANAGERS AND PROJECTIONISTS 


249 


tre charging top hole prices, and have watched a scene per¬ 
haps containing huge buildings sway backward and forward, 
because the management had failed to properly support the 
screen by a framework, but were using a painted drop 
weighted at the bottom by a wooden strip, with result that 
every time there , was an extra strong current of air the 
screen moved to and fro. 

TRAVELING EXHIBITORS may carry a painted cloth 
screen or metallized surface screen successfully, always pro¬ 
vided it be rolled face inward on a round wooden rod not less 
than 3 or 4 inches in diameter, and further provided that a 
clean muslin sheet be spread over the surface of the screen 
before it is rolled, this in order to protect the surface from 
dirt which may accummulate on the back of the screen. A 
painted screen rolled on such a support (which latter may be 
made up by nailing thin wooden strips, such as lattice work 
is made of, around round wooden end and center supports) 
will not be very bulky and its surface will not crack. Of 
course if the screen is to be shipped by express, then an 
outer wooden covering would necessarily have to be made 
for it. 

CAUTION.— The screen should be rolled as tightly as pos¬ 
sible in order to prevent the surfaces rubbing against each 
other in transit. 

FIREPROOFING SOLUTION.— Any screen or other fabric 
may be fireproofed by thoroughly saturating it with am¬ 
monia phosphate, mixed in the proportion of one pound to 
one gallon of water. In applying the solution to a cotton 
screen it should first be tightly stretched on a frame and the; 
solution applied with a cheap paint brush, prior to the appli¬ 
cation of the glue sizing. Let the fireproofing dry thoroughly 
before applying the glue size. 

Fabric which has been thoroughly saturated with ammonia 
phosphate solution will char, but it will not and cannot be 
made to blaze. If you hold a lighted match against the 
fabric the result will be a hole charred in the cloth—that is 
all. There is nothing in ammonia phosphate that will in any 
way injure the fabric. Wood thoroughly soaked in the solu¬ 
tion is made fireproof in the sense that it cannot be made to 
blaze. 

STRETCHING THE SCREEN.— The wide use of metallic 
surface screens, many of which are constructed of heavy 
cloth or canvas, makes it very difficult to stretch them tight- 


250 


HANDBOOK OF PROJECTION FOR 


ly, though tight-stretching is necessary since with a semi- 
reflective surface every wrinkle or uneven place will show 
badly. 

There is nothing better for this purpose than what is 

known as the “artist 
frame.” It is very much 
superior to any home¬ 
made arrangement, and 
may be purchased from 
almost any screen 
manufacturer for less 
than it would cost an 
exhibitor to make it. It 
is simple, and we be¬ 
lieve quite satisfactory. 
It may be shipped 
knocked down, and the 
process of putting it 
together is one which 
can be readily per¬ 
formed by any man of ordinary intelligence. 

Begin to put the frame together by laying it bottomside 
up, on a floor, or other flat surface. After the corners are 
bolted together see that the whole frame is exactly square. 
This may be tested by measuring diagonal corners. If the 
distance from diagon¬ 
ally opposite corners 
is equal the screen, as 
a whole, is square. 

Next, put on the back 
braces and then turn 
the frame over, or set 
upright in place. The 
various steps in the 
process are shown, in 
their order, in Fig. 71. 

PUTTING ON 
CLOTH. — The cloth 
should be rolled up so 
that the edge that goes 
to the top unrolls first. It may be put on either with the 
frame standing up or lying down. Standing the frame up¬ 
right is the best plan, however, because the cloth will partly 
stretch by its own weight, and the whole job will be more 







MANAGERS AND PROJECTIONISTS 


251 


easily and better done. A good start is a long step toward 
success. Lay the roll of cloth on a level floor, unroll a foot 
or two, and stretch a chalk line to determine whether or not 
its edge is perfectly straight. Trim it if necessary to fit the 
chalk line. Now make a chalk line across near the extreme 
edge of the top of the frame, on the front side, where the 
cloth is to be tacked. The straight top edge of the cloth and 
the line on frame are placed together and the cloth is tacked 
fast, thus insuring a good, straight start. 

TACKING ON CLOTH.— Place the tacks about two inches 
apart. A thin tack with a large, flat head is the best. If the 
frame is placed upright a piece 
of cheese cloth should be looped 
and nailed to the frame on each 
end, to hold the roll of cloth in 
position while the top edge is 
tacked in place. Start at the 
center of the top, and tack both 
ways along the chalk line, until 
within about three or four feet 
of the corner. A single tack 
will hold each corner in position 
until you are ready to tack 
corners. Now unroll cloth slow¬ 
ly and carefully, keeping it 
stretched at all times. Stretch 
and tack the bottom of screen, 
beginning at center and working 
again to within three or four 
feet of each corner. Next tack 
one side from center to within 
a short distance of corner, and 
then tack and stretch the cloth 
on the other side, after which 
finish up the corners. 

In tacking any cloth screen 
always begin at centers of top, bottom and each side, and 
finish corners last. 

If the work is done carefully the surfaces will be almost 
entirely free from wrinkles, and where a light cloth is used 
and well stretched by hand a very even surface is possible 
on a common hand-made frame. The artist frame we are 
describing is provided with finishing strips which are added 
in order to cover up the tacks and raw edge of the cloth, 





252 


HANDBOOK OF PROJECTION FOR 


which helps the appearance very much. Beveled stretcher 
strips are then pushed down between the cloth and frame 
from the back, giving the appearance of a bevel around 
the edge on the face side. This gives a handsome, finished 
appearance to the screen generally. 

In most cases the cloth is free from wrinkles when the 
stretcher strips are put in position, but to provide for fur¬ 
ther stretching lag bolts are placed in the frame which, 
when screwed in, push out the stretcher strips still farther, 
so that the screen can be made as tight as a drumhead. 
The artist frame is always good property, as it can be used 
again for new cloth. Those exhibitors who use metallized 
screens should renew them at least every two years. Many 
metallic screen surfaces lose their brilliancy in even less 
time, and often those of inferior quality will become dull 
within a few months. Fig. 69 shows front of finished screen. 

SIDE VIEW DISTORTION.— The effect of viewing the 
screen at heavy angle should be, but apparently is not, 
thoroughly understood by architects. To a person seated at 
an extreme side angle to the screen all figures thereon ap¬ 
pear to be abnormally tall and very thin. The explanation 
for this is very simple. 



Figure 72. 



MANAGERS AND PROJECTIONISTS 253 

In Fig. 72 we view a theatre screen E F, A B an object 
in the picture on the screen, and C and D the eyes of two 
spectators, one seated directly in front of and the other at 
a wide angle to the surface of the screen. C of course sees 
object A B at its full width, but, remembering that the ob¬ 
ject on the screen is only an image, hence absolutely level 
or flat, it is evident that D will get the effect only of width 
B G. This explains the apparent lack of breadth in the 
object. The effect of abnormal tallness is, however, 
partly due to the foreshortening of the width of the 
object. We have been accustomed to seeing a man or 
woman of a given height have, within certain limitations, a 
certain given breadth. If we foreshorten the breadth un¬ 
naturally the effect is to give the impression of greatly 
added height. 

Another reason for the apparent tallness is that it is real¬ 
ity. The figures on a screen are often very much taller than 
in real life. This is not realized because they have the cus¬ 
tomary proportions. If, however, the breadth be foreshor¬ 
tened until a figure ten feet tall has only the width of a 
normal man or woman the effect is a ridiculously tall, thin 
caricature of the original. 

The lesson taught by this is that patrons should not be 
seated at too wide an angle to the screen. Architects may 
readily determine exactly what the effect in foreshortening 
of width will be at any given angle by applying the simple 
process shown in Fig. 72. 

DISTORTION — KEYSTONE EFFECT. — The distortion 
of the picture and its outline caused by the projection lens 
being out of center with the screen is commonly termed 
“keystone effect,” because of the fact that when the pro¬ 
jection lens is considerably above the center of the screen 
(the condition most commonly met with) the picture outline 
assumes, in greater or less degree, according to the condi¬ 
tion, the shape of an inverted keystone. 

This is illustrated in Fig. 73, in which A is the projection 
lens, B C the screen, E F a horizontal line perpendicular (at 
right angles) to the surface of the screen at its center, B D 
the position screen B C must assume in order that its sur¬ 
face be perpendicular to (at right angles with) the axis of 
projection, D C the distance lower margin of the light beam 
must travel in order to reach the screen surface in excess 
of distance travelled by the upper margin. The solid lines 
of H show the resultant shape of picture on the screen, and 


254 


HANDBOOK OB PROJECTION FOR 


the broken lines what the picture should be and would be 
were lens A located at E, or screen B C in position B D. 
Observe that the picture will be wider at the bottom and 
narrower at the top than it would be were the axis of pro¬ 
jection along line E F—the projection lens central with the 
center of the screen. Analyzing Fig. 73 we find approxi¬ 
mately as follows: Distance of projection being 80 feet and 
the width of the picture 16 feet at its center, it would, under 
normal conditions be twelve feet high. Since the picture is 
192 inches (16 feet) wide, the beam must spread out 192 
inches divided by 80 feet equals 2.4 inches for every foot of 
projection distance. Distance D C is 3 feet 8 inches, or 3.66 
feet, hence with the screen in perpendicular position the 



beam must travel 3.66 feet further in order to reach the 
lower edge of the screen than to reach its top. It there¬ 
fore follows that the beam will be 3.66x2.4 inches=8.786 
inches wider at its bottom than at its top, and proportion¬ 
ally all the way up and down the picture, thus producing the 
shape known as “keystone,” shown by solid lines at H, Fig. 
73. 

Fig. 74 gives us the number of inches drop in projection 
per foot of distance when the angle is 12 degrees. It is 2.55 
inches. If it is proposed to have the lens a certain height 
above screen center, and a given distance from the screen 
(distance of projection) it is only necessary to multiply the 
projection distance, in feet, by 2.55 to know whether the 
angle will be more or less than 12 degrees. If the result is 
greater than the proposed height of the lens above screen 
center, measured in inches, the angle is less than 12 degrees. 










MANAGERS AND PROJECTIONISTS 


255 


For instance: Proposed projection distance 60 feet. Pro¬ 
posed height of lens above screen center ten feet (120 
inches). 2.55x60=153, hence at 60 feet the lens must be 153 
inches above screen center to produce a 12 degree pitch. 
Its proposed location is less than that, hence the angle will 
be less. 

PROJECTION ANGLE NOT SAFE GUIDE.— The Society 
of Motion Picture Engineers has set 12 degrees from a hori¬ 
zontal line passing through the center of the screen (it is 
not so stated, but presumably that is what is meant) as the 
maximum permissible angle of projection. This, as is shown 
in Fig. 74, means a horizontal rise of 2.55 inches each foot 
of projection distance. 

Let us examine the matter. Assuming a 96-foot projec¬ 
tion distance, a 12-degree angle and a 16-foot picture, we 



find that the beam will spread just 2 inches per foot. Using 
a similar angle and the same size picture, but a 50-foot 
projection distance, we find the spread of the beam to be 3.8 
inches per foot, but since both the angle and picture size 
remain constant, distance D C, Fig. 73, will remain un¬ 
altered, and since the spread per foot of the beam is greatly 
altered by the changed distance of projection, the resultant 
distortion of the picture will be very much greater on the 
short projection distance than on the long. Hence we say 
that angle of projection is not always a safe guide. 

In our opinion the only reliable guide to permissible pro¬ 
jection angle is the amount of distortion a given condition 
will produce, and up to this time no competent authority has 
undertaken to say what amount of distortion may be toler¬ 
ated. It must be remembered that the resultant distortion 















256 


HANDBOOK OF PROJECTION FOR 


is present all over the image. It is not confined to the pic¬ 
ture outline, but alters the relative width of things in dif¬ 
ferent portions of the picture, as well as making the whole 
picture and everything in it abnormally tall. In fact this 
latter is the worst feature of the distortion. Outline distor¬ 
tion may be corrected by filing the aperture plate opening. 
Distortion of width of objects in the picture usually is not 
very noticeable, but added height is very readily discernible. 

Fig. 75 illustrates the effect of projection distance on 
projection angle, height of projection lens above screen re¬ 
maining the same. If the lens be located 25 feet above 
screen center, and the projection distance 40 feet, the pro¬ 
jection angle will be 32 degrees. With the projection dis¬ 
tance 80 and 120 feet respectively, the projection angle is 



reduced to 17 degrees and 20 minutes, and 11 degrees and 46 
minutes. 

It is the opinion of the author that picture height offers 
the best and safest guide to permissible projection angle, 
and that any projection room location which increases the 
normal height of the picture by more than 5 per cent, is ob¬ 
jectionable and should not be tolerated. 

It will be observed that this permits an increase of the 
height of a sixteen-foot-wide picture by a trifle more than 
seven inches, so that at 80 feet projection distance a 15-de¬ 
gree angle would be within the limit by .2 of an inch. This 
would automatically add a maximum of 5 per cent, to the 
height of all objects on the screen, including the actors, so 
that a six-foot man who happened to appear just life size in 

















MANAGERS AND PROJECTIONISTS 


257 


a normal size picture would appear as being 6 feet, 3.6 
inches tall; also his head would be smaller in proportion 
than his feet, though this latter, if confined within this 
range, will not injure the results perceptibly. 

While the following figures are not exactly correct, they 
are nearly enough so for our purpose. 

Given a projection distance of 80 feet, the following pro¬ 
jection angles will increase the height of a 16-foot-wide pic¬ 
ture as follows : 

Angle of 10 degrees increases height 4.5 inches. 

Angle of 15 degrees increases height 7 inches. 

Angle of 20 degrees increases height 13 inches. 

Angle of 25 degrees increases height 20 inches. 

Angle of 30 degrees increases height 32 inches. 

WHEREIN THE EVIL OF DISTORTION LIES.— The 

average exhibitor, and very many unthinking projectionists, 
believe that so long as the sloping sides of a distorted pic¬ 
ture are made perpendicular, which may be done (see Filing 
the Aperture below), there is no remaining evil except 
the added difficulty of obtaining sharp focus all over the 
screen. They base their belief on the fact that the theatre 
patrons do not know or realize that the picture is distorted, 
hence no harm is done. 

This is fallacious reasoning. Admitting the fact that if the 
sides of the distorted picture be made perpendicular, the 
audience, having nothing as a basis for comparison, prob¬ 
ably will not know the distortion is present, the fact remains 
that the distorted picture is not nearly so pleasing to the 
eye as the undistorted* one, or the one only slightly distorted, 
and since theatre patrons pay admissions to theatres in or¬ 
der that they may be amused and entertained, it follows that 
the more pleasing the appearance of the picture as a whole, 
aside from its merits as a play, the better satisfied the 
patron will be, and the better satisfied the patron is, the 
more he is likely to patronize the box office frequently. 

FILING THE APERTURE. —Side lines of Keystone may be 
made parallel by filling side of aperture with hard solder or 
procuring special aperture plate from projector manufacturer 
and filing sides to suit. First project light to screen and make 
mark on screen at lower ends of top corner curves. Then 
remove aperture and fill in sides or substitute special aperture. 
Next place a metal plate over the lamphouse cone, in the 


258 


HANDBOOK OF PROJECTION FOR 


center of which is a hole about of an inch in diameter 
Next hang cords at the screen so that they will pass down 
exactly over the marks you have made at the bottom of the 
upper corner curves. Now strike an arc, and, with the light 
through the hole in the plate over the cone to guide you and 
show you the exact effect of every move, file out the aper¬ 
ture sides until the light comes exactly to the lines on the 
screen. 

The light enables the worker to watch the exact effect of 
every stroke of the file. He is thus enabled to do a very ac¬ 
curate job. It is necessary to be extremely careful in filing 
because if you get a bit too much metal off at any stroke of 
the file it means the job must all be done over again. 

Keystone effect is invariably accompanied by a greater or 
less tendency to out of focus. This is especially true if it be 
side keystone, since the picture is wider than it is high. It 
is caused by the fact that a projection lens is presumed to 
focus at a given distance, (Fig. 36 D), and since with distortion 
of the kind we have described the distance to the screen 
varies, it will readily be seen that a strain is placed on the 
powers of the projection lens in the matter of focusing. The 
lens may be given increased depth of focus, or in other 
words may be caused to focus over a greater distance by re¬ 
ducing its diameter, and this is why large diameter objec¬ 
tives are a very hard proposition to handle where there is 
any decided tendency to distortion in the way of keystone 
effect. If the projectionist is working under conditions of 
heavy distortion or keystone and is unable to get a sharp 
focus all over his picture, let him try stopping down the 
diameter of his projection lens by inserting a ring of black 
cardboard in the front end of the lens barrel, right up 
against the front factor of the projection lens. In the cen¬ 
ter of this cardboard cut out a circle say one inch in 
diameter. If this sharpens the picture, then he can know 
where the trouble lies and can increase the size of the hole 
in the stop until the trouble again appears, after which a 
new metal disc with an opening just a little bit smaller will 
serve the purpose. We know of no other means of remedy¬ 
ing such a condition, so long as the distortion remains, and 
the remedy we have suggested may be quite expensive in 
light, therefore it is a waste of electric current. 

CHARACTERISTICS OF SCREEN SURFACES.—The 

following data is extracted from a paper presented to the 
Society of Motion Picture Engineers by Lloyd A. Jones and 


MANAGERS AND PROJECTIONISTS 


259 


Milton F. Fillius, contained in the Dayton transactions of 
the society. The data contained is the result of three com¬ 
plete sets of readings made by two different men, of each 
surface tested, so that apparently the liability of error is 
very small indeed. It is greatly to be regretted that kalso- 
mine and paint surfaces were not tested, but the data never¬ 
theless marks a very distinct step forward, since it provides 
the exhibitor and projectionist with a basis for intelligent 
comparison, as well as data which should enable him to 
select a screen surface suitable for use in the individual 
theatre by some other method than guess work, statements 
of salesmen or personal observation, none of which methods 
have very much value. 

In making the comparisons a magnesium carbonate sur¬ 
face was selected as a basis, and its power of reflection was 
given an arbitrary value of 100 per cent. The reflection 
value of all other surfaces is therefore given as the per¬ 
centage of reflection power of the magnesium carbonate 
surface. 

In Table I is given a complete list of the materials meas¬ 
ured. 

The surface of the magnesium carbonate sample (1) was 
prepared by carefully scraping a block of the material with 
a steel straight-edge. The opal glass (2) was of the best 
quality obtainable for uniformity and whiteness, and the 
surface was carefully ground. The white blotting paper 
(3) was of the ordinary commercial quality used extensively 
in photographic work. The photographic stock (4) was a 
sample of uncalendered and uncoated material. No. 5 was 
of the same material but treated with the ordinary baryta 
coating. The drawing paper (6) was the commercial grade 
of Wattman’s hot pressed. Sample No. 7 was prepared by 
sandblasting a sheet of aluminum. No. 8 was made* by sand¬ 
blasting the front surface of an ordinary plate glass mirror. 
No. 9 consists of a screen made by superimposing a sample 
of the material such as is commonly used as the focusing 
screen in photographic apparatus upon the surface of an 
ordinary plate glass mirror. 

The commercial screens examined and tested also are 
listed in Table II, beginning with No. 10. In the name 
column of Table II will be found the trade name applied to 
the surface by its manufacturer, in the texture column a 
qualitative statement* of the character of the surface, and in 
the color column a qualitative statement of the color of the 


260 HANDBOOK OF PROJECTION FOR 

surface. Let it be understood, however, that the terms used 
in describing texture and color are very general in their 
nature, as no precise qualitative measurements were made of 
these characteristics. 

CLASSIFICATION OF SURFACES. —An examination of 
the characteristics of the screens examined and tested show 
they may be roughly grouped into three general classes, A, 

TABLE 12 


No. 

Class 

Name 

Texture 

Color 

1 

C 

Magnesium Carbonate 

Smooth 

White 

2 

C 

Opal Glass 

Smooth 

White 

3 

C 

White Blotting Paper 

Smooth 

White 

4 

c 

Photo Stock Plain 

Smooth 

White 

5 

c 

Photo Stock Coated 

Smooth 

White 

6 

c 

White Drawing Paper 

Smooth 

White 

7 

B 

Sandblasted Aluminum 

Smooth 

Metallic White 

8 

A 

Sandblasted Mirror 

Smooth 

White 

9 

A 

Focus Screen and Mirror 

Smooth 

White 

10 

A 

Superlite 

Coarse Grain 

Metallic White 

11 

A 

Special 

Coarse Grain 

Metallic White 

12 

B 

Green Back 

Fine Grain 

Metallic W 7 hite 

13 

B 

White Back 

Fine Grain 

Metallic White 

14 

C 

Plain White Coated 

Smooth 

Yellow 

15 

A 

Imsco Silver No. 1 

Coarse Grain 

Metallic White 

16 

A 

Imsco Gold No. 1 

Coarse Grain 

Metallic Yellow 

17 

A 

Imsco No. 2 

Coarse Grain 

Metallic White 

18 

A 

Imsco No. 3 

Medium Grain 

Metallic White 

19 

B 

Imsco No. 4 

Fine Grain 

Metallic White 

20 

C 

Imsco White Muslin 

Smooth 

White 

21 

A 

Minusa A 

Medium Grain 

Metallic White 

22 

A 

Minusa B 

Coarse Grain 

Metallic White 

23 

A 

Minusa C 

Coarse Grain 

Metallic White 

24; 

A 

Mazda-Lite 

Fine Grain 

Metallic White 

25 

B 

Idealite-Grade 1A 

Fine Grain 

Metallic White 

26 

B 

Idealite-Grade IB 

Medium Grain 

Metallic White 

27 

B 

Idealite-Grade 2 

Fine Grain 

Metallic White 

28 

C 

Dalite Crystal White 

Smooth 

Blue Green 

29 

B 

Dalite Gold Fibre 

Fine Grain 

Metallic Yellow 

30 

A 

Dalite Silver 

Fine Grain 

Metallic White 

31 

A 

Argus Crystal Bead No. 1 

Medium Glass Eeadf 

Yellow 

32 

B 

Argus Crystal Bead No. 2 

Fine Glass Beads 

Yellow 

33 

B 

Mirroroid 

Fine Grain 

Metallic White 

34 

A 

Gold Ring 

Smooth 

Metallic Yellow 

35 

C 

Half-tone 

Smooth 

White 

36 

A 

Aluminium Paper 

Smooth 

Metallic White 


B and C. Class A includes all those surfaces reflecting a 
large proportion of the picture light within a very narrow 
angle, and very little, by comparison, at greater angles. 
Class C includes those screens having high diffusive power 
and in Class B are grouped those surfaces which are inter¬ 
mediate between the extremes represented in classes A 
and C. 

















MANAGERS AND PROJECTIONISTS 


261 


It should, however, be clearly understood that the line of 
demarkation between the three classes is not distinct. The 
classification is entirely arbitrary, and is made for the pur¬ 
pose of practical convenience. 

CAUTION. —In examining and considering the data here 
tabulated the exhibitor and projectionist should remember 
that two items only are considered, viz.: the reflecting 
power of the surface and its relative reflection at varying 
angles, and that while these two things are of first impor¬ 
tance, still there are other very desirable physical charac¬ 
teristics to be considered when the final selection of a screen 
is to be made. It may be found, for instance, that two or 
more surfaces are equally efficient for a certain auditorium, 
insofar as concerns reflective power and evenness of light 
distribution, but that one of them is found to have other 
characteristics superior to its competitors, such as a more 
substantial foundation (cloth backing) or the mounting or 
guarantee given with it. In such a case the final selection 
would of course be made on these latter points, reflection 
and distribution being equal. 


TABLE 13 

MISCELLANEOUS SURFACES 


DEGREES OF ANGLE 


No. 

0 

5 

10 

15 

20 

30 

40 

50 

60 

70 

1 

100 

100 

99.9 

98.0 

96.9 

94.9 

92.4 

89.5 

84.8 

78.8 

2 

77.1 

77.1 

76.0 

76.0 

74.8 

73.7 

73.7 

72.6 

70.5 

68.2 

3 

68.9 

67.9 

65.9 

64.0 

63.0 

60.8 

59.7 

57.2 

54.8 

54.2 

4 

73.9 

73.9 

71.2 

70.0 

67.0 

65.0 

63.5 

62.2 

61.1 

58.4 

5 

91.1 

88.0 

84.9 

82.5 

80.5 

79.3 

78.7 

78.7 

76.9 

74.3 

6 

82.7 

82.7 

81.5 

77.8 

74.4 

72.0 

69.5 

63.3 

67.6 

65.4 

7 

66.3 

64.1 

61.4 

57.6 

52.4 

46.5 

40.1 

36.0 

35.3 

32.6 

8 

473 

399 

297 

224 

121 

62.0 

40.2 

34.2 

32.0 

31.1 

9 

460 

430 

373 

257 

176 

73.3 

31.9 

20.5 

19.0 

19.4 


In Table No. 13 we have the characteristics of the first 9 
surfaces in Table No. 12, none of which are commercial 
screens, but surfaces prepared for testing purposes. Select¬ 
ing No. 1 for example, which by reference to Table No. 12, 
we find to be magnesium carbonate (the surface used 
for comparison), we find that, taking its reflective power at 
100 when we stand directly in front of it, it shows 100 per 
cent, when we move to one side to an angle of five degrees, 























262 


HANDBOOK OF PROJECTION FOR 


but at 10 degrees it has lost 1/10 of one per cent, of its bril¬ 
liancy. At a 15 degree angle it has lost 2 per cent, of its 
brilliancy as viewed from straight in front or at an angle of 
5 degrees. At 20 degrees its brilliancy drops to 96.9, or a bit 
more than 3 per cent., and so on until at the extreme angle 
of 70 degrees it has lost 21.2 per cent, and has 78.8 per cent, 
of the brilliancy shown from straight in front. On the other 
hand, taking surface No. 8, which we see by Table 11, is a 
sandblasted mirror, we find that from straight in front it has 



a reflective power of 473 as compared with 100 for magne¬ 
sium carbonate. In other words, the sandblasted mirror 
has reflective power almost four times that of magnesium 
carbonate when viewed from directly in front. If, however, 
we examine it at an angle we find that up to and somewhat 
beyond a 20 degree angle it retains its superiority over mag¬ 
nesium carbonate, though in rapidly decreasing percentage, 
but that somewhere between 20 and 30 degrees it drops be¬ 
low the magnesium carbonate, and at 30 degrees it has only 





















MANAGERS AND PROJECTIONISTS 


263 


62 per cent, of its brilliancy, while at an angle of 70 degrees 
its brilliancy has dropped tc 31.1 per cent. Remember that 
all these percentages are percentages as compared to mag¬ 
nesium carbonate. In other words, it has enormous “fade¬ 
away” when viewed at an arcrle, though up to about 25 de¬ 
grees it, while reflecting far below its straight-in-front bril¬ 
liancy, still is equal to the magnesium carbonate surface, 
and anywhere within that range it is superior. 

And now let us see exactly what that means. In Fig. 76 
we have the representation of an auditorium 80 feet wide by 
70 feet front to back. The individual can select the side lines 
which fit the width of his own theatre. Each of the small 
squares is 10 feet each way. 

TABLE 14 

COMMERCIAL SURFACES TESTED 


DEGREES OF ANGLE 


No. 

0 

5 

10 

15 

20 

30 

40 

50 

60 

70 

10 

268 

256 

215 

168 

120 

64.8 

34.3 

21.8 

16.8 

14.2 

11 

300 

284 

255 

206 

167 

93.9 

52.2 

26.5 

17.0 

13.3 

12 

208 

203 

188 

161 

134 

85.0 

533 

330 

22.4 

18.3 

13 

177 

174 

165 

143 

122 

85.9 

53.0 

330 

23.8 

17.7 

14 

72-9 

72-2 

70.8 

70.5 

60-4 

68.9 

68.1 

68.8 

67.0 

640 

15 

286 

273 

229 

173 

129 

66.0 

33.0 

21.4 

15.2 

13.7 

16 

311 

288 

234 

180 

125 

66.0 

35.0 

21.7 

156 

14.0 

17 

230 

220 

200 

171 

141 

83.1 

474 

296 

20.3 

16.0 

18 

208 

197 

177 

152 

127 

80.6 

47.9 

34.3 

24.3 

19.9 

19 

186 

183 

160 

146 

120 

79.8 

47.9 

313 

22.2 

17.6 

20 

664 

66.3 

652 

636 

62.4 

61.0 

60.4 

60.0 

59.3 

58.9 

21 

326 

308 

270 

204 

157 

780 

386 

25.7 

15.0 

12.5 

22 

355 

339 

274 

207 

149 

71.7 

35.8 

21.7 

15.0 

12.8 

23 

315 

298 

256 

203 

151. 

77.9 

38.9 

230 

16.1 

130 

24 

334 

323 

276 

215 

160 

82.9 

100 

24.5 

16.6 

138 

25 

154 

151 

136 

112 

97.0 

75.1 

56.0 

52.9 

47.0 

43.0 

26 

193 

187 

154 

i24 

98.5 

72.2 

58.4 

502 

45.2 

40.9 

27 

142 

137 

122 

103 

93.6 

76.4 

63.7 

556 

50.8 

46.8 

28 

71 7 

71.7 

708 

609 

60.2 

68.6 

671 

66.0 

65.3 

64.8 

29 

126 

120 

116 

104 

90.7 

68.8 

47.1 

34.3 

26.5 

21.9 

30 

183 

172 

157 

134 

107 

650 

421 

28.8 

20.9 

16.8 

31 

244 

240 

177 

116 

75.6 

45.5 

40.0 

39.6 

41 .7 

43.7 

32 

140 

138 

113 

91.4 

78.6 

60.9 

54.8 

50.8 

50.4 

50.0 

33 

142 

138 

120 

100 

99.0 

73.4 

49.5 

35.7 

27.4 

22.5 

34 

292 

271 

216 

160 

198 

49.2 

28.4 

17.4 

13.1 

9.7 

35 

78.6 

78.6 

74.9 

733 

71.1 

68.6 

65.3 

63.9 

62.3 

59.5 

36 

148 

136 

111 

93.6 

74.1 

50.2 

34.1 

26.5 

22.6 

19.5 


In table 14 we see that the angle of highest efficiency lies 
either within or very near to 20 degree lines for ordinary 
commercial screens, and that beyond 30 degrees all the sur¬ 
faces except 14, 20, 28 and 35 (which same have low reflec- 




















264 


HANDBOOK OF PROJECTION FOR 


tive and high diffusive power) fall off very rapidly, none of 
them standing much above 50 per cent, at 50 degrees angle. 
We may therefore conclude that for all the high reflective 
surfaces tested the range of efficiency lies well within the 
50 degree angle, and it must be considered that beyond 
30 degrees the difference between screen brilliancy in 
different sections of the house is such that it is apt to be 
noted by patrons, though this may be to some extent bal¬ 
anced by the preference some patrons have for a more or 
less brilliant picture. 

Applying Fig. 76 let us suppose the exhibitor to have a 
house 40 feet wide by 70 feet deep. We have indicated a 16-foot 
wide picture by the thick black line. Following the 20 de¬ 
gree angle lines through the auditorium we see that consid¬ 
ering a single point at the center of the screen at 20 feet 
from the screen, a space considerably less than 20 feet wide, 
or less than half the width of the house, falls within that 
angle, and even the 40 degree angle does not take in the en¬ 
tire width at 20 feet from the screen. At 30 feet from the 
screen the 30 degree angle does not take in the entire width 
of the house, whereas the 20 degree angle only includes a 
little more than 20 feet of its width. 

But we consider only a point at the center of the screen, 
whereas the screen is 16 feet wide, so that the angle will 
include 8 feet more space on one side, but the patron seated 
on that side will be just that much worse off insofar as has 
to do with the other half of the screen. 

Our purpose, however, is to indicate how Fig. 76 should 
be applied in practice, rather than to draw conclusions, since 
we shall, later, give you the conclusions arrived at by those 
making the tests. We give you Fig. 76 and we give you 
the tables showing the characteristics of the various sur¬ 
faces. The rest is up to you, insofar as application of the 
data to your own local condition be concerned. 

Remember that each one of the horizontal lines in Fig. 
76 represents 16 feet of front to back depth, while each per¬ 
pendicular line represents 10 feet of auditorium width. 

The makers of the test drew their own conclusions, which 
same we shall present verbatim, and with no more com¬ 
ment than may be necessary to make the meaning clear. 

CONCLUSIONS ARRIVED AT.— In order to facilitate 
the examination of the data, it will be well to separate them 
into their respective classes. After careful consideration of 
the characteristics of the screens and of the requirements of 


MANAGERS AND PROJECTIONISTS 


265 


practical use, it was decided to define the range covered by 
these classes as follows: 

Class A includes those screens which are adapted for use 
in theatres where the maximum angle of observation does 
not exceed 30 degrees; Class B includes the screens adapted 
for use where the maximum angle of observation does not 
exceed 50 degrees, while the Class C screens should be used 
in all cases where the angle of observation is greater than 
50 degrees. The point should be again emphasized that 
these classifications are not rigid, but of an approximate 
character. 

TABLE 15 
CLASS A 


Sur¬ 

face 

20° 

30° 

40° 

50° 

No. 

Ratio 

R 

Ratio 

R 

Ratio 

R 

Ratio 

R 

8 

3.91 

305 

7.62 

235 

11.8 

194 

IS.8 

165 

9 

2.61 

339 

6.30 

270 

14.4 

217 

22-4 

183 

34 

2.70 

209 

5.94 

167 

10.3 

137 

16.8 

116 

31 

3.22 

159 

5.48 

127 

6.10 

108 

6.17 

96 

22 

2.38 

265 

4.96 

216 

9.92 

167 

16.3 

151 

15 

2.21 

218 

4.34 

178 

8.70 

147 

13.4 

134 

21 

206 

253 

4.30 

207 

8.47 

172 

13.2 

145 

10 

2.23 

205 

4.14 

169 

7.82 

140 

12.3 

119 

24 

2.08 

253 

4.02 

209 

8.35 

174 

13.6 

147 

23 

2.08 

245 

4.00 

201 

8.10 

167 

13.7 

141 

11 

1.80 

242 

3.20 

202 

5.75 

172 

11.3 

147 

16 

1.69 

228 

3.20 

181 

6.03 

152 

9.75 

130 

36 

2.00 

112 

2.96 

96.4 

4.34 

833 

5.59 

732 

30 

1.70 

151 

2.82 

128 

4.35 

110 

6.36 

87 

17 

1.63 

192 

2.77 

165 

4.85 

141 

7.77 

121 

18 

1.64 

172 

2.58 

150 

4.25 

128 

6.07 

112 


Note: Columns marked “R” indicate mean (average) reflecting power 
within the entire angle. 


After careful consideration of the subject, it was decided 
that the value of the ratio of the reflecting power measured 
at normal observation to that measured at the maximum 
angle of observation in a particular installation would serve 
as the most logical criterion by which to select the most 
suitable screen for any particular case. 

This value will then represent the ratio of the brightness 
of the screen as observed by a person in the center of the 
auditorium to that of the brightness as observed by a person 
occupying a seat at the side and near the front. By keeping 
this ratio below a certain limiting value, satisfactory bright¬ 
ness will be obtained for all observers. This factor alone, 
however, is not sufficient for the classifying of screens ac- 



















266 


HANDBOOK OF PROJECTION FOR 


cording to their relative merits. The highest average re¬ 
flecting power within the required angle from the normal 
will necessitate the least energy expenditure in the project¬ 
ing system to produce a given screen brightness. 

Assuming cases in which the maximum angles of observa¬ 
tion are 20 degrees, 30 degrees, 40 degrees, and 50 degrees the 
values of the ratio of the reflecting power at normal observa¬ 
tion to that at these various angles were computed for all 
screens and likewise values of mean reflecting power for the 
same limiting angles. These values are tabulated for the 
Class A screens in Table 15, those for the Class B screens in 
Table 16, and those for the Class C screens in Table 17. 

TABLE 16 
CLASS B 



20° 

30° 

40° 

50° 

No. 

R« 

Ra 

Ro 

Ra 

Ro 

Ra 

Ro 

Ra 


R*20 

Rso 

R40 

Rso 

12 

1.55 

179 

2.45 

155 

3.91 

135 

6.30 

117 

19 

1.55 

161 

2.34 

141 

3.88 

129 

5.95 

109 

13 

1.45 

156 

2.06 

139 

3.34 

121 

5.37 

106 

33 

1.43 

123 

1.93 

111 

2.87 

99 

3.97 

88 

26 

1.96 

151 

2.67 

131 

3.30 

115 

3.70 

104 

29 

1.39 

111 

1.83 

100 

2.68 

90 

3.68 

79 

25 

1.59 

130 

2.05 

115 

2.75 

104 

2.91 

94 

32 

1.78 

112 

2.30 

99 

2.56 

89 

276 

82 

27 

1.52 

120 

1.86 

108 

2.23 

98 

2.56 

91 

7 

1.26 

60.3 

1.42 

56.7 

1.65 

53.5 

1.84 

50.4 


Now it seems reasonable to demand that the ratio of the 
brightness on the axis to that at the extreme angle of obser¬ 
vation sholl not be greater than 4.0. This value is decided 
upon after consideration not only of the variation in bright¬ 
ness as observed from various points in the auditorium, but 
also from a consideration of the fact that from a given 
point of observation the screen may appear of unequal 
brightness over its area. The danger of this inequality be¬ 
ing serious increases rapidly as the value of the above men¬ 
tioned ratio in reflecting powers increases. Assuming now 
that we adopt the value of 4 as the limiting value of the re¬ 
flecting power ratio, it is possible from the figures in Tables 
15, 16 and 17 to choose the best screen for any one of the 
cases considered. For instance, assuming that the maximum 
angle of observation is 20 degrees, it will be noted that all 

















MANAGERS AND PROJECTIONISTS 


267 


values in the under 20 degree ratio column of Table 15 are 
less than 4. Therefore from the standpoint of distribution 
any one of the screens in Class A will be satisfactory for 
use where the angle of observation does not exceed 20 de¬ 
grees. In order now to obtain the maximum average, bright¬ 
ness within this angle for a minimum current consumption it 
is only necessary to choose that screen, or screens, which 
shows the highest value in the column marked R. Next, 
assuming a maximum angle of 30 degrees we find that the 
first seven screens, Table 15, are excluded since the ratio of 
normal to extreme reflecting power is greater than 4. Be¬ 
ginning with No. 11 we may then choose screens showing 
the highest average reflecting power for the range 0 to 30 

TABLE 17 
CLASS C 


No. 

20° 

30° 

40° 

50° 

Ratio 

RmSO 

Ratio 

Rm30 

Ratio 

Rm40 

Ratio 

Rm50 

6 

1.10 

79.8 

1.15 

77.7 

1.19 

76.1 

1.30 

74.6 

35 

1.10 

75.3 

1.14 

73.5 

1.20 

71.7 

1.23 

704 

3 

1.09 

65.8 

1.13 

64.6 

1.15 

63.5 

1.20 

62.5 

4 

1.10 

71.2 

1.13 

69.6 

1.16 

68.3 

1.19 

67.3 

5 

1.13 

85.4 

1.15 

835 

1.15 

82.7 

1.15 

82.0 

1 

1.03 

90.0 

1.05 

97.9 

1.08 

96.8 

1.12 

95.5 

14 

1.05 

71.0 

1.06 

71.0 

1.07 

70.0 

1.07 

67.0 

20 

1.06 

64.0 

1.09 

64.0 

1.10 

52.0 

1.10 

54.0 

28 

1.02 

71.0 

1.03 

70.0 

1.04 

70.0 

1.07 

69.0 

2 

1.03 

77.1 

1.05 

76.2 

1.05 

75.6 

1.06 

750 


degrees. (Author’s Note : This average was found by add¬ 
ing together reflector powers for 0, 5, 10, 15, 20 and 30 de¬ 
gree angles and dividing by 6.) When the maximum angle 
of 40 degrees is considered we find no screen in Class A 
which does not exceed the limiting value of 4 for reflecting 
power ratio. We therefore turn to Table 16, and there find 
that all values of the reflecting power ratio are less than 4. 
We may therefore select from Class B that screen which has 
the highest reflecting power for the 0 to 40 degree range. In 
case of the 50 degree limiting angle, three of the Class B 
screens are automatically excluded, and it is only necessary 
to select from the remainder the one having the highest 
average reflecting power for the 0 to 50 degree angle. 















268 


HANDBOOK OF PROJECTION FOR 


The Film 

T HE film is a strip of celluloid 1J4 Inches wide by from 
to 6 one thousandths of an 'inch in thickness. In 
the process of making the celluloid is originally in 
strips about 2 feet wide by 250 to 300 feet in length. These 
wide strips are passed through a machine which spreads 
upon one side a coating (negative or positive, according to 
the use to which the stock being treated is to be put) of 
photographic emulsion. The emulsion is a part of the thick¬ 
ness of the film as above given. 

Having received its emulsion coating the film is passed 
through another machine which splits it into ribbons 1J4 
inches wide, and these ribbons become the film stock which 
is purchased by the photoplay producer. 

The negative stock is first perforated, then it is placed in 
a camera having an intermittent movement, a revolving 
shutter and a lens, the whole mechanism being very similar 
in its action to that of the motion picture projector, except 
that the mechanism and film are enclosed in a light tight box, 
or casing. Each 24 of an inch of the negative is successively 
exposed to the light by the camera mechanism, and what is 
nothing more nor less than a “snapshot” photograph is im¬ 
pressed thereon. The exposures are supposed to be at the 
rate of 16 per second, but in practice camera speed varies 
over a rather wide range, running as high as 80 feet of film 
to the minute in some instances. 

After exposure the negative is removed from the camera, 
developed, fixed and dried by much the same chemical proc¬ 
ess as is any ordinary Kodak negative, though the me¬ 
chanical methods necessarily differ widely from the Kodak 
process, since the negative film will be anywhere from ten 
to 300 feet in length. 

The negative is then projected to a screen, so that the 
director may check up his work, make the scene over again 
if necessary, or cut out any undesirable portions. When 
the negative is finally in acceptable form it is placed in a 
printing machine in contact with a strip of positive film 
(positive and negative film are precisely the same, except 
that a different grade or kind of photographic emulsion is 


MANAGERS AND PROJECTIONISTS 


269 


used) and by means of another intermittent movement and 
revolving shutter, but without the lens this time, it is ex¬ 
posed to artificial light of fixed, known power, each picture 
being exposed for the small fraction of a second. The posi¬ 
tive film is then developed, fixed and dried, after which it is 
sent to the assembling room, where the various scenes con¬ 
stituting a complete photoplay are arranged in sequence, 
joined together, the titles and sub-titles inserted, and it 
finally becomes the “reel of film” with which we are all 
familiar. 

The foregoing, of course, only very roughly describes the 
various processes through which the film passes in the 
course of its making and the making of the play. To de¬ 
scribe all the processes in detail would require a book of 
goodly size in itself. 

The perforating usually is done by the producer, though 
perforated stock may be purchased from the film stock 
maker. There are 64 perforations to the foot on either side, 
or 4 on each side to each picture. Of late years film per¬ 
foration has been brought up to a state of almost absolute 
mechanical perfection. It is one of the processes which 
must be done with great accuracy, else there will be un¬ 
steadiness of the picture on the screen. 

THICKNESS OF FILM STOCK.— It is important that 
film stock be of unvarying, standard thickness, since thin 
stock has a decided tendency to produce unsteadiness of the 
picture on the screen, besides being unduly weak and short 
lived. 

STANDARD PERFORATION AND OTHER FILM 
MEASUREMENTS.— At present (1922) there are several 
shapes of sprocket hole; also the dimensions of various 
sprocket holes vary. The Society of Motion Picture Engi¬ 
neers has adopted as standard the dimensions shown in 
Fig. 77. 

We quote the following from a paper read by Donald 
Bell before the Society of Motion Picture Engineers at its 
New York City meeting in 1916. Mr. Bell is, we believe, the 
best living authority on such matters. 

“It is accepted as settled fact that the maximum shrinkage 
of motion picture film is .0937 of an inch per foot. Painstaking 
experiment warranted the conclusion that a gauge length of 
11.968 inches for 64 holes would insure that accuracy of 
perforation necesary to perfect results, and at the same 
time make due allowance for the shrinkage of film. The 


270 


HANDBOOK OF PROJECTION FOR 


following computation shows why we have adopted 11.968 
inches instead of 12 inches as the standard for a perforation 
gauge measuring 64 holes : 

“Assuming the outside diameter of the sprocket of all 
standard projectors to be .9375 (15/16) of an inch, then the 
circumference would be 2.94525 inches. As a standard motion 
picture film has an average thickness of .0065 of an inch, the 
pitch diameter of the sprocket will be found to be .9375 of 
an inch, plus .0065 of an inch, or a total of .944 of an inch. 

“Pitch circumference is 3.1416 x .944 = 2.965704 inches Cir¬ 
cular pitch equals 2.965704 h- 16 (number of teeth on a 
sprocket) = .1853+ of an inch. 

“The standard perforating gauge being 11.968 inches for 64 



holes, and the 
maximum a 1 - 
lowance for 
shrinkage be- 
ing .09375 
(3/32) of an 
inch fo r 64 
holes, there- 
fore 11.968 
inches minus 
.09375 of an 
inch, or 11.8743 
inches, is the 
average length 
o f shrunken 
film measuring 


Figure 77. , , s P rock et 

holes. The 

film or length per hole, is 11.8743 divided by 64, or ‘.l&JKo/an 
inch. Pitch of sprocket .1853 of an inch. Pitch of film 18855 
of an inch. 


Pitch means distance from center to center 
The dimensions shown in Fig. 77 represent‘good practice 
and it is to be hoped that in the near future all film dirnen- 
sions including the sprocket holes, will be thoroughly 
standardized along these lines. 8 y 

DAMACIE T ° FILM.— When film is new, pliable and de¬ 
cidedly tough, its celluloid base is at that time least sus- 

the nW T age ’ b r’. ° n the other hand - that is the time 
:ir t0 *l* Ph Z emu,s,on ,s most easily damaged. By un¬ 
intelligent handling of the film, lack of care in the adjust- 






































MANAGERS AND PROJECTIONISTS 


271 


ment of the projector, improper lining of the two elements 
of the rewinder, too-rapid speed of rewinding and the im¬ 
proper storing, great damage is caused, which mounts into 
the tens of thousands of dollars a day, and this unnecesary 
damage must, in the very nature of things, be added to the 
“overhead” expense of the industry, and finally be paid for 
in the form of increased film rentals. 

A very large percentage of the scratches in the photogra¬ 
phic emulsion of film, which same fill up with dirt and 
form the “rain” with which we are all familar, is caused by 
improper rewinding, particularly the process known as 
“pulling down.” 

This latter consists of holding one reel stationary while 
the other is revolved to tighten the film roll, which operation 
causes all the various layers of film to slip upon each other 
under much friction, and since there are always more or less 
particles of dust and dirt adhering to the film, scratches are 
the inevitable result. 

Injury to sprocket holes is, for the most part, due to under¬ 
cut or hooked sprocket teeth (see general instruction No. 
7, Page 602) to too much pressure by the tension shoes 



Figure 77A 







272 


HANDBOOK OF PROJECTION FOR 


of the projector (see general instruction No. 9, Page 603) 
and to excessive takeup tension. 

As a general proposition we believe that most projectionists 
and some operators are at least reasonably careful in hand¬ 
ling and repairing film. In many theatres, however, re¬ 
winding, threading the projectors and repairing film is made 
the duty of a more or less irresponsible usher or reel boy, 
whose main idea is to get the job finished in the least pos¬ 
sible time. These boys do not understand the damage done 
by careless work; also undoubtedly many of them do not 
care. If a splice is to be made, their one and only idea is 
to get the film ends stuck together. In their view the quick¬ 
est way is the best way, regardless of after-results. Badly 
matched splices, misframes, splices without the emulsion 
scraped off or only partly scraped off are the regular thing 
where an usher or reel boy does the repairing. It is no un¬ 
common thing where this sort of irresponsible help is placed 
in charge of repairing film for an exchange to receive film 
back “spliced” with a nail or a pin. Even when the pro¬ 
jectionist does the rewinding and repairing he is, in all too 
many cases, expected to do it while projecting a picture, 
hence must neglect either one thing or the other. 

In the majority of cases the real underlying fault is in the 
failure of the theatre management to employ sufficient com¬ 
petent help in the projection room. Film repairing should, 
under no circumstances, be done by any other than a thor¬ 
oughly competent, responsible projectionist or a regularly 
employed projectionist apprentice. 

Injury to film in passing through a modern motion picture 
projector is invariably due either to the bad condition of the 
film itself, to the false economy of a theatre management 
which refuses necessary repairs to the projector, or to the 
lack of knowledge, carelessness or laziness of the pro¬ 
jectionist himself, which results in improper tension adjust¬ 
ment, hooked sprocket teeth, etc. 

Film exchange managers seem, in all too many cases, not 
to realize that the sending out of film in poor condition not 
only is an outrage against the producer, against the pro¬ 
jectionist who must use it, against the theatre management 
which is paying for films in good repair, but also against the 
audience which pays money to see at least a reasonably per¬ 
fect performance. The average exchange manager does not 
seem to understand that sending out film in poor condition 
is a direct invitation to more and greater damage, since a 


MANAGERS AND PROJECTIONISTS 


273 


loose splice is likely to catch on a sprocket idler and split 
anywhere from one to four feet of film before the projector 
can be stopped, especially in houses where the projectionist 
is obliged to rewind and do other chores while his projectors 
are running the show. 



Splices in which sprocket holes are not properly matched 
are likely to clamp the sprocket teeth, thus causing a jump 
in the picture and per¬ 
haps the loss of a loop, 
or they may grip the 
teeth of the sprocket and 
wrap around it, particu¬ 
larly if the sprocket 
teeth be under cut or 
somewhat hooked. Split 
sprocket holes will oft- 
times catch on a sprocket 
idler, and a section of the 
edge of the film will split 
off, even if nothing worse 
occurs. 


EMULSION DEPOSIT. 

—Much damage is done 
to first run film by means 
of emulsion deposit (see 
general instruction No. 
10, Page 604). This 
trouble is greatly aggra¬ 
vated if the projectionist 
carries too tight a gate 
tension. 


In fact there are num¬ 
berless ways in which 
film may receive damage. 

It is a fragile product, bigme 77B 

and a product which 

must be in absolutely perfect condition if there is to be a 
perfect picture on the screen. 


FILM WAXER. —When using first run films upon which 
the emulsion is soft there is always the inclination of emul¬ 
sion to rub off and deposit on the tension shoes or springs. 
The best method of preventing this is to place a small 
amount of suitable wax on the sprocket hole tracks. 


274 


HANDBOOK OF PROJECTION FOR 


There are at least two excellent machines on the market 
which accomplish this purpose, viz.: “The Werner film 
waxer, illustrated in Fig. 77A made by the Werner Film 
Projector Manufacturing Company, St. Louis, Mo., and the 
Weiss Film Waxer, made by Adam Weiss, Cleveland, Ohio. 



Figure 77C 



This latter is illustrated in Fig. 77B. Both are very efficient 
devices. 

It is quite possible to make a home-made waxer which will 
work very well. Such a device is illustrated in Fig. 77C. 
The construction of the device is made clear in the illus¬ 
tration. Ordinary tallow candles may be used or cylinders 
of wax may be made by using a tin mould of suitable 
diameter, open at both ends. Pour this full of melted 

paraffine wax, which 
may be had at any drug 
store and most grocery 
stores. Let it cool and 
then slightly heat the 
receptacle whereupon 
the wax cylinder may 
be pushed' out. 


Figure 77D 

Humidor can for film. May be used 
for keeping film pliable, or for re¬ 
saturating old, dry film with moisture, 
though if used for the latter purpose film 
must be wound very loosely. 


MENDING THE 
FILM, i. e., making 
splices in it, is a matter 
deserving of very much 
more consideration 
than it apparently has 
received. 

Poorly made splices 
are a source of great 
and unending annoy- 

















MANAGERS AND PROJECTIONISTS 


275. 


ance to all concerned, as well as the source of literally 
enormous damage to film. 

It has even been claimed by competent projectionists that 
badly made splices are a greater source of damage to film 
than all other things combined. And there is good ground 
for their claim, too, because a poorly made splice may cause 
damage in many ways, not the least of which is to start a 
film split, which may continue for several feet before the 
projector (and the show) can be stopped. 

One source of very great annoyance is the imperfect 



Figure 77E 

A and C are broken sprocket holes improperly notched, C being very 
bad, indeed. B is properly notched except that the notch spreads too 
wide and weakens adjoining holes. D and E are examples of atrociously 
made splices. D is half an inch wide and not properly scraped. F is 
crooked and E is an example of slovenly work in scraping the emulsion 
off. G is a mis-frame and is otherwise improperly made. 

matching of sprocket holes so common where splices are 
made by hand. Imperfectly matched sprocket holes are apt 
to cause the following troubles: (a) Picture jumps as the 
splice goes through because the sprocket holes are too small 
to allow sprocket teeth to set properly, hence film is lifted 
away from the sprocket, (b) A too-small sprocket hole lock- 











276 


HANDBOOK OF PROJECTION FOR 


ing on sprocket tooth and pulling film around under sprocket, 
(c) Film running off sprocket, (d) Intermittent sprocket 
teeth “climbing” one or more holes, thus shortening or 
“losing” one of the loops, and throwing the picture out of 
frame on the screen, (e) Side movement of picture due to 
crookedness of film as a whole, (f) Takeup,. pulling film over 
lower sprocket, thus shortening or losing the lower loop. 

All this is apt to occur, even though the sprocket holes be 
perfectly matched on one side, if they be imperfectly 



Figure 77F 

A is a splice which may cause sprocket holes to clamp sprocket teeth, 
with consequent jump of picture on screen, or even the pulling of the 
film around sprocket. It certainly will cause side movement of picture 
on screen. At B is a broken sprocket hole which has been improperly 
notched, proper shape of notch being shown at D or F, though notches D 
and F are correct as to shape only. They should not have been made 
either in or so near a splice. As the injuries to the film now are all 
that portion ,from A to D should be cut out and a new splice made. At 
G a splice is necessary because the injury includes three successive 
sprocket holes. 


matched on the other side, because in that event the hole or 
holes on one side will be small, and the film, as a whole, will 
be crooked at that point. 

You will therefore see the great importance of matching 





MANAGERS AND PROJECTIONISTS 


277 


the sprocket holes perfectly, which in practice means using 
either a splicer or some sort of metal teeth for a guide. 

In many projection rooms the practice is to make splices 
with the unaided fingers. Film cement welds, more than it 
glues the film together, hence evenly applied pressure, of 
considerable amount, is necessary to the making of a per¬ 
fect joint, and while it is quite possible to apply sufficient 
pressure with the fingers, it certainly cannot be applied 
evenly, with the almost inevitable result that even though 
the finger-made splice be strong in part of its width, it will 
be weak in another part. 

In Fig. 78 you see a compact and very effective film splicer. 
It is made by the General Machine Company, New York 
City. We have had 
this device tested and 
have tested it person¬ 
ally. It is excellent 
and well worth its 
price, which latter is 
quite reasonable. We 
advise the installation 
of this device or a / 
similar one in all pro¬ 
jection rooms, and 
that the making of * 
hand-made splices be Figure 78. 

absolutely prohibited. 

WIDTH OF SPLICE. —A too-narrow splice is apt to be 
weak, and a too-wide one objectionably stiff. Provided a 
good film splicer be used, there is no necessity for a splice 
of greater width than .125 (J4) of an inch. Such a splice will 
be amply strong and at the same time sufficiently flexible to 
go through the projector without any indication of its pres¬ 
ence in the film showing on the screen. 

There has been a machine used by some producers which 
makes a splice about 1/32 of an inch wide. There is no 
practical advantage in the use of such a splice in positive 
film, and these very narrow splices have been an unending 
source of annoyance to the projectionists. The maker of the 
machine places the blame on those handling it, but that is 
no excuse, because a machine which does not function well 
in the hands of the employees who must be depended on to 
handle it is not a good machine, notwithstanding the fact 
that it would produce good results if expertly operated. 



278 


HANDBOOK OF PROJECTION FOR 


Anyhow, as we have said, there is no advantage in such a 
narrow splice in positive film. 

There should always be one full sprocket hole in the stub 
end, as at A, Fig. 79, and stub end A should never exceed 
.125 ( l /&) of an inch in width, unless it be necessary to 
slightly exceed that width in order to avoid cutting into the 
sprocket hole. 

MAKING THE SPLICE.— Cut the film ends as per Fig. 79, 
end B being trimmed exactly on the dividing line (frame 
line) between two pictures, the other end with a stub end 
(A Fig. 79) extending .125 (J4) of an inch beyond the frame 
line indicated by dotted line. 

It is of the utmost importance that every particle of emul¬ 
sion be scraped off stub end A; also that the back, or cellu¬ 
loid side of end B be scraped lightly in order to roughen the 
celluloid and remove all dirt and grease. 



Figure 78A. 


Some prefer a very sharp knife blade and some a safety 
razor blade fixed in a convenient holder, to scrape with. What 
is used does not matter, provided a thorough job be done, 
without removing any appreciable portion of the celluloid 
itself, since that would weaken the film stock. 

OF IMMENSE IMPORTANCE.— It must be understood 
and remembered that the emulsion covers the entire film, 










































MANAGERS AND PROJECTIONISTS 


279 


from outside to outside, and that, except for special cements, 
film cement will not adhere to emulsion, and will not pene¬ 
trate it and weld the celluloid beneath—for film cement does 
not merely stick the surfaces of the film together, but 
actually welds them, if the cement be a good one. And this 
is right where the greatest sin is committed in making 
splices. 



B 


0 0 0 0 

0 0 0 0 < 

IIP 


0 0 0 0 

0 0 0 o £ 


Either from laziness, carelessness or lack of time to do the 
job right, or because they fear to break the edge of the film 
at the sprocket hole, many do not scrape the emulsion off 
thoroughly, or even do not scrape it off at all around the 
sprocket holes, RIGHT WHERE THE HEAVIEST STRAIN 
ON THE SPLICE WILL COME. The inevitable result is 
that such splices either never are cemented together at their 
edges, or else very quickly come loose at the sprocket holes, 
whereupon there is, sooner or later (usually sooner), trouble. 

SCRAPE TO A STRAIGHT LINE.— Stub end A, Fig. 79, 
should be scraped to a straight line at the frame line, as per 
dotted line, and the use of a straight edge is imperative to 
this end. Too much trouble? Well, if you think so, then 
you ought not to be allowed to handle film at all. Careless¬ 
ness in this respect means flashes of white light on the 
screen. 

Having scraped the end of the film as directed, apply 
cement all over the scraped surface of stub end A, but do 
not smear on too much, because surplus cement is very apt 
to adhere to the tension shoes and cause trouble. The 















280 


HANDBOOK OF PROJECTION FOR 


actual method of placing the ends together will, of course, 
vary according to whether or not a splicer is used, but in any 
event one must work fast, match the sprocket holes of the 
two ends perfectly, and then apply tolerably heavy and 
evenly distributed pressure for say five seconds. 

Every cement bottle should have a small brush, the handle 
of which is attached to the under side of the cork, or else 
thrust through it. When you buy cement, accept none with¬ 
out the brush, unless you already have an empty bottle thus 
equipped. 

FILM CEMENTS. —The Eastman Kodak Company has on 
the market a film cement which is, so they assert, made from 
tested chemicals, which means that every lot will be exactly 
the same. This cement is equally good for either inflammable 
or non-inflammable film. Certainly the Eastman company, 
being the largest manufacturers of film in the world, ought 
to know what is required in a film cement, and if tested chem¬ 
icals only are used, that should be sufficient guarantee to us 
all that the cement is good. 

We, therefore, recommend to you the cement made by 
the Eastman company. You may get further information in 
an advertisement we are advised they propose to run in the 
back of the book. 

FORMULAS. —In presenting there formulas please under¬ 
stand we do NOT vouch for their excellence. They are all 
good when made from' proper chemicals, but experience has 
amply proven the fact that when a certain formula for film 
cement is made up at different times from chemicals purchased 
from various local drug stores, there not infrequently is a 
wide variation in results. We therefore present cement 
formulas subject to that notation. 

ORDINARY. —For non-inflammable stock, pound of 
acetic ether, l /± pound of acetone merch, in which dissolve 
6 feet of non-inflammable film from which the emulsion has 
been removed. (See Removing Emulsion, Page 290.) 

For inflammable film, a piece of the film 3 inches long 
dissolved in 1 ounce of acetic ether is a satisfactory cement, 
but it will not work on N. I. (non-inflammable) stock. In 
dissolving the film, in either case, first remove the emulsion 
and then cut the film into fine strips. 

ACETONE CEMENT.— Four ounces of acetone; ounce 
ether; 6 inches old film, from which remove the emulsion 
and cut into strips. 


MANAGERS AND PROJECTIONISTS 


281 


ANOTHER FORMULA.— Equal parts of amyl acetate and 
acetone. Will not turn white on film, and will not dissolve 
the film as ether will. Works on all kinds of stock. Best 
used with an all steel 3 flap film mender. Can be used 
by those making patches by hand if worked rapidly. Scrape 
film, use small camel hair brush; keep bottle tightly corked 
when not in use. 

STILL ANOTHER.— One ounce collodion; 1 ounce banana 
oil or bronzing liquid; y 2 ounce ether. For Pathe hand 
colored films, y 2 acetone and y 2 ether. 

N. I. CEMENT.—For non-inflammable film add 1 part 
glacial acetic acid to 4 parts of flexible collodion to any of 
the film cements. It is satisfactory for either N. I. or 
regular film. 

FILM REEL CONSTRUCTION.— Immense amount of 
damage has been done to film in the past by reason of the 
flimsy construction of reels. The earlier practice was to use 
a wooden hub 1 y 2 inches in diameter, upon which was 
mounted two rather flimsy, more or less open, metal reel 
sides. The hub itself had little stability, its diameter was 
absurdly small, and the reel sides entirely inadequate to 
withstand the abuse to which they were, in ordinary prac¬ 
tice, subjected. 

Of late years there has been a tendency to increase the 
diameter of the hub to about 5 inches, and to make it of 
metal instead of wood. The sides of most reels we have 
as yet seen are still entirely too flimsy. They bend too 
easily, and a bent reel is a prolific source of damage to film, 
not only by reason of the fact that there is the possibility 
of the bent reel rubbing on the sides of the upper magazine, 
thus acting as a brake and subjecting the film to a heavy 
strain between the upper sprocket and the reel, particularly 
at the last end of the run, but also by reason of the fact 
that the bend may be inward, thus pinching the film between 
the two sides, both while being projected and in the process 
of rewinding. 

In order to save in first cost of reels and shipping weight, 
film exchanges have favored a light weight, flimsily built, 
cheap reel, notwithstanding the fact that the damage done 
to film by small hubs and bent reel sides, amount to many 
time the “saving” accomplished by the foolish proceduce. 

We strongly recommend to exhibitors that they equip 
their projection rooms forthwith with a full complement of 
the best reel obtainable, and that, if necessary, they oblige 


282 HANDBOOK OF PROJECTION.FOR 

their projectionists to use them. (See Projection Room Reels, 
page 322.) 

In considering this recommendation exhibitors should re¬ 
member that all damage to film which tends to shorten its 
useful life must inevitably come back to the exhibitor in 
the form of increased film rental, hence the less damage done 
to the films while in their theatre the less will be the gen¬ 
eral overhead expense to be charged back in this way. 

SIZE OF REELS. —The present trend is to use 2,000 foot 
reels in the process of projection, though for the most part 
film is still shipped on 1,000 foot reels. In considering 
whether it is the better practice in projection to use 1,000, 
2,000 or 3,000 foot reels, we must take into consideration the 
fact that it sometimes is better to go around a stone wall 
than to climb it or try to push it over with your hands. The 
1,000 foot reel offers a somewhat less liability to damage 
in the process of rewinding and handling, and a less pos¬ 
sibility of fire loss in case of fire at the projector, but the 
fact remains that in the majority of large modern theatres 
2,000 foot reels are used in projection. That is the condition, 
and we may as well make the best of it. We do not mean 
to infer by this, however, that there is any very serious 
objection to a 2,000 foot reel, since with modern projectors 
fires are of rare occurrence, and as a general rule the 2,000 
foot reel (not film, but the reel itself) is kept in better con¬ 
dition than is its smaller brother, so that perhaps the added 
tendency to damage in rewinding with small reels in poor 
condition is thus counterbalanced. There is, it seems to us, 
no real need for a 3,000 foot reel, and there are very serious 
objections to its general use. 

But whatever the capacity of the reel, one thing is im¬ 
portant, viz.: Its sides should always extend over the film 
roll by at least % and preferably y 2 an inch, because in this 
way the whole film roll will be protected by the metal sides 
of the reel. The overloading of reels has been a source of 
much annoyance to projectionists and great damage to film, 
though this particular evil is not so much practiced of late. 
Even film exchanges are apparently slowly learning to ex¬ 
ercise a little horse sense, in some directions at least, in the 
care of their property. The evil of the overloaded reel is 
three-fold, (a) That portion of the film outside, or above 
the sides of the reel, is absolutely unprotected, hence liable 
to injury in many ways other than the likelihood of its 
slipping off, to the exasperation of the projectionist and the 


MANAGERS AND PROJECTIONISTS 


283 


possible delay of the show while it is being wound on again, 
to say nothing of probable damage through contact with a 
more or less dirty, dusty floor, (b) (Very serious indeed) 
the increased temptation to “pull down,” and pull down good 
and hard, too, in order to get as much of the film inside the 
reel sides as possible, (c) The fact that the film may rub 
against the magazine, thus scratching it and possibly inter¬ 
fering seriously with the operation of the takeup, inci¬ 
dentally requiring an excessively tight takeup tension, which 
is worse than bad, and a prolific source of damage to the first 
part of the film through scratching and the tendency to pull 
the film over the teeth of the lower sprocket, thus injuring 
the sprocket holes, scratching the film and losing the 
lower loop. 

HOW MUCH FILM WILL A REEL HOLD?— We have 
been asked many times how to figure what number of feet a 
reel of given diameter, with a hub of given diameter, will hold. 

This is a question which cannot be answered exactly, be¬ 
cause it will depend upon how tightly the film is wound. It 

is possible to figure it, though we cannot recommend the 
process for accurate results. 

First find average length of film layers, which is done by 

adding together the circumference of the reel hub and the 

outside circumference of the film roll, when the reel is full, 
and dividing the result by two. The result will be the average 
length, in inches, of all layers of film. 

Next subtract half the diameter of the reel hub from half 
the diameter of the film roll. The result will be the number 
of inches of film, or the “depth” of the film roll from outside 
diameter to hub. 

Next you may either count the number of layers of film 
in one inch, or you may divide 1,000 by 6 (six thousandths of 
an inch being the thickness of film and emulsion), which will 
give you the number of layers of film per inch, provided the 
film be very tightly wound. Counting is best, though, and 
even that will be unreliable, because of variation in tightness 
of winding. 

You now multiply the number of layers of film per inch 
by the number of inches of depth in the film roll, and multiply 
that result by the average length of the layers. Divide this 
by twelve, to reduce to feet, and the final result will be the 
number of feet of film on the reel, or which a reel will hold, as 
closely as it can be figured. 


284 


HANDBOOK OF PROJECTION FOR 


LEADER AND TAIL-PIECE.— For several reasons it is 
essential that there be a “leader” and “tail-piece” at the ends 
of every reel of film, including the multiple reel feature. 
The leader not only serves to protect the title from dam¬ 
age, but it enables the projectionist to thread his projector 
with one of the first frames of the main title over the aper¬ 
ture, whereas otherwise by the time the projector was 
threaded much of the main title would be past the aperture. 
Then, too, in threading into the takeup it is frequently de¬ 
sirable, if not necessary, to fold an inch or so of the film 
over on itself. By so doing it is made stiffer and more easily 
thrust under the reel spring, also it is more certain to “stay 
put.” This means that the film will soon break off where 
it is folded, which causes a gradual wasting away of . the 
main title, if there be no leader, and soon there will either 
not be sufficient title, or a new one will have to be provided 
for. If, however, there is a leader, then there is no wasting 
of the main title, and leader costs very much less than title. 
Another reason why leader should be used is that at the end 
of the process of rewinding the film often slaps around any¬ 
where from one to a dozen times before the reel is stopped, 
and if there be no leader to receive the brunt of this rough 
treatment the title itself is injured. Leader should be at 
least 36 inches long, and 5 feet is very much better. Old 
film may be used for leaders, but the better plan is to use 
film upon which no photograph has been impressed, but 
which has been exposed in the printing and developed quite 
dense. This has the advantage of allowing the man who is 
too lazy to thread in frame to frame up before the main 
title comes on. 

As a matter of fact no competent projectionist who has 
pride in his work will even think of threading out of frame, 
but there are a considerable number of operators, or mis¬ 
called projectionists, who still persist in sloppy methods. 
They have no pride in their work, and no right place in a 
projection room. Instead of being paid for their work the 
motion picture industry would do better to, if necessary, pay 
them to remain entirely outside of all projection rooms. 

Let us here remark that some projectionists use a stere- 
opticon title where the film title is too short to show. A 
better plan than this is to punch a hole about of an inch 
in diameter in the center of the dowser, then before starting 
the projector, with the dowser down and the revolving 
shutter of the projector turned until the projection lens is 


MANAGERS AND PROJECTIONISTS 


285 


open, raise the automatic fire shutter and project the film 
title to the screen. If the hole in the dowser be not too large 
(% inch in diameter ought to do the trick all right) there 
will be absolutely no danger of injury to the film, and at the 
same time the title will appear on the screen plenty plain 
enough to be read by the audience. It is a much better plan 
than using a stereopticon slide. 

Our reason for advising a leader and tail-piece on multiple 
reel features is found in the fact that whereas they will 
slightly inconvenience the projectionist of the large theatre, 
who joins his 1,000 foot reels together in 2,000 foot reels, 
they will be very necessary to the projectionist who projects 
from 1,000 foot reels. 

AN OPAQUE TAIL-PIECE is of great importance, be¬ 
cause we know of nothing in all the realm of projection so 
thoroughly disillusioning as the flashing of white light on the 
screen at the end of a reel. The careful, competent pro¬ 
jectionist will stop his projector, or will change over to the 
other projector before the end of the reel comes. This man will 



Figure 79A. 

Graphic illustration of a reel rightly rewound A, which may only be 
done by applying considerable and even brake friction to the reel from 
which the film is being rewound, and a reel improperly rewound, which 
means without the tension supplied by brake action on reel from which 
film is being wound. Film rewound as per reel B is liable to serious 
damage in several ways. It is “pulling down” to tighten films rewound 
as per B which causes nine-tenths of the “rain.” 




286 


HANDBOOK OF PROJECTION FOR 


need no tail-piece, but the sloppy man who either does not 
care or is too lazy to do his work right, and who lets the end 
of the film pass the aperture before changing over to the sec¬ 
ond projector should have an opaque tail-piece on all his reels, 



Figure 79B. 

At A we see an improperly packed shipping case. Resultant possible 
damage to the films is apparent. At B we see a properly packed 
shipping case. Remarks seem unnecessary. 

so that instead of the screen going white it will go dark, 
provided, of course, he is sufficiently on the job to stop the 
projector while the tail-piece is over the aperture. 

The allowing of the entire film to run through and the 
flashing of the white light on the screen at the end of the 
run is very crude work indeed, so crude that no man de¬ 
serving the title projectionist would even think of doing it. 
Even the “operator” should be ashamed to do such a stupid 
thing. 

FILM INSPECTION—The projectionist should, so far as 
is practicable, repair all damage, other than ordinary wear 
he himself inflicts upon film while it is in his possession. 

It is the duty of film exchanges to thoroughly inspect and 
repair all films before they are sent to a theatre. THE 
PRICE EXHIBITORS PAY FOR FILM INCLUDES THIS 
SERVICE, AND WHEN AN EXCHANGE FAILS TO PER¬ 
FORM IT. IT JUST TO THAT EXTENT IS NOT DOING 
ITS DUTY, MODIFIED ONLY BY THE FACT THAT IN 
OCCASIONAL INSTANCES WHERE THERE IS IN- 









MANAGERS AND PROJECTIONISTS 287 

SUFFICIENT TIME TO MAKE REPAIRS THE EX¬ 
CHANGE MAY BE EXCUSED, PROVIDED IT PLACES 
IN THE BOX WITH THE FILMS A CARD STATING 
THAT THE FILMS HAVE NOT BEEN EXAMINED AND 
REPAIRED, AND INSTRUCTING THE PROJECTIONIST 
TO MAKE REPAIRS, SENDING TO THE EXCHANGE 
HIS BILL FOR THE SERVICE. 

BY NO STRETCH OF IMAGINATION CAN IT BE 
DEEMED THE DUTY OF THE PROJECTIONIST TO RE¬ 
PAIR FILMS RECEIVED FROM AN EXCHANGE, AND 
WHEN, IN CASE OF EMERGENCY, IT IS NECESSARY 
FOR HIM TO DO SO, HE HAS THE PERFECT RIGHT 
TO EXPECT TO BE PAID BY THE EXCHANGE, AT A 
REASONABLE RATE PER HOUR, FOR HIS SERVICE, 
SINCE HE IS NOT A FILM INSPECTOR AND REPAIR 
MAN, BUT A PROJECTIONIST. 

PERFECT PROJECTION IS IMPOSSIBLE OF AC¬ 
COMPLISHMENT UNLESS THE FILM BE ITSELF IN 
PERFECT MECHANICAL CONDITION, AND A FILM IS 
NOT IN PERFECT MECHANICAL CONDITION WHEN 
IT HAS WIDE, STIFF, OR LOOSE SPLICES, MIS- 
FRAMES, STRAINED OR RIPPED SPROCKET HOLES 
RAIN, ETC., OR WHERE ITS SURFACE IS SMEARED 
WITH OIL. THESE FAULTS ARE PROLIFIC SOURCES 
OF POOR SCREEN RESULTS. 



Figure 80. 


It is a well known fact that many film exchanges make 
only the most superficial inspection of film, and either very 
little or no repairs at all. The underlying cause of this is, 
we believe, an endeavor by film exchanges to get too much 
work out of the film, coupled with a deliberate attempt 
on the part of the exchange to force the projectionist to do 


288 


HANDBOOK OF PROJECTION FOR 


their film inspection and repair work free of charge, be¬ 
cause they are unwilling to expend the necessary amount of 
money in. the employment of either enough or competent in¬ 
spectors. In many exchanges we can personally bear testi¬ 
mony to the fact that “inspection” and repairs consist of a 
man or girl rewinding the film at top speed, stopping only 
when the film is torn clear in two. We might incidentally 
add that these “inspectors” often used crooked reels and re¬ 
winders which are badly out of line, under which condition 
by rapid rewinding of the film they actually do more damage 
to the film than their “repairs” amount to. 

The ordinary exchange inspection does not detect any¬ 
thing except the very worst faults, such as long stretches 
of ripped sprocket holes, a patch loose half way across the 
film or the film torn entirely in two. Minor faults cannot 
possibly be detected by the whirlwind inspection process in 
vogue in very many exchanges. 

We are well aware that the question of inspection and 
repair presents a problem of several angles, and one which 
is not at all easy to adjust. However, the statement that 
there is absolutely no excuse whatsoever for the utterly 
miserable condition in which many films are received by 
the projectionist cannot be successfully contradicted. 

We are heartily in favor of projectionists demanding 
overtime for inspecting and repairing film when they are 
received in bad condition. We are unable to understand by 
what process of reasoning either the exhibitor or exchange 
justifies his demand that the projectionist do' the work 
without remuneration. 

FILMS ON A CIRCUIT.—Where films are used on circuit 
it should be a point of honor with each projectionist to send 
the films away in as good condition as they are received, 
DON’T leave it to your brother projectionist who gets them 
next to repair the damage YOU have done. 

FILM NOTCHING PLIERS.— For a long time there has 
been on the market a cutting plier with which broken 
sprocket holes may be notched as per Fig. 80. 

This tool should be in the hands of every exchange in¬ 
spector and projectionist. It is the invention of A. Jay 
Smith, Cleveland, Ohio. 

WHERE TO KEEP FILMS.— Film should be kept near 
the floor of the projection room, since near the ceiling it is 
much warmer. It should be kept in a metal box having com- 


MANAGERS AND PROJECTIONISTS 


289 


partments for each reel, and one compartment below to hold 
a wet sponge or water. The film should be treated with a 
little glycerine once in a while, but this is. only accomplished 
by having the film in actual contact with the liquid, as per 
directions further on. The glycerine is for the purpose of 
keeping the film soft and pliable, which it does by reason of 
the fact that it has the property of rapidly absorbing and 
retaining moisture. 

Should water, by any accident, be spilled over a reel of 
film, or it even be dropped in a pail of water, it may be saved 
from damage if unrolled very quickly, not allowing the 
emulsion, which will be quickly softened, to touch anything. 
But the unrolling must be done very quickly or the emulsion 
will stick to the back of the film and pull off. This does not 
apply to colored or tinted film, though even these may some¬ 
times be saved by very prompt action. The author once 
rescued a first-run film from destruction thus: He happened 
to be in the projection room after the show had closed for 
the night. In taking the last reel from the magazine it slip¬ 
ped from the projectionist’s hands and landed in a pail of 
water, being practically submerged. He grabbed the reel, 
ran down stairs, handed the end to an usher, ran to the front 
end of the theatre, looped the film over a chairback, and ran 
back and forth until the whole film lay across the back of 
the seats. The emulsion became very soft in places, but next 
morning it was found that a total of less than five feet was 
damaged. The exchange men never knew of the occurrence 
until more than a month after, when they were told of it. 

MOISTENING DRY FILM. —Traveling exhibitors often 
find that a film which has been a long time in use has be¬ 
come very dry and brittle. It may be remoistened and ren¬ 
dered pliable by unwinding into a large metal can, in the 
bottom of which water has been placed, with a wire screen 
over it to keep the film from contact therewith. Cover 
tightly, set in a moderately warm place until the film is soft 
and pliable. Watch closely, however, since if made too 
moist the emulsion will stick to the back of the film when 
it is rewound. 

It is even possible to give a film a glycerine bath, as fol¬ 
lows : In a shallow pan a few inches wide by 6 feet long 
place a solution of 30 parts of clear water to one part of 
glycerine. Make a drum of slats about six feet in diameter 
by about six feet long (for one thousand feet of film), and 
by revolving the drum draw the film very slowly through 


290 


HANDBOOK OF PROJECTION FOR 


the liquid, winding on the drum with the emulsion side out. 
After the film is all on the drum, revolve it rapidly to throw 
off the surplus liquid, then continue to revolve the drum 
slowly until the film is dry. It should not be used for two 
or three days. Perform this operation in a room entirely 
free from dust, or you may seriously injure your film. 

Due to lack of proper exchange inspection it is usually 
necessary to inspect the films at the theatre before 
they are run. To do this place the reel on rewinder, and 
rewind it very slowly, holding the edges between the thumb 
and forefinger with pressure enough to cup it slightly. By 
so doing you instantly detect all stiff or loose patches. Cut 
out the stiff ones and remake. Cement all loose patches and 
notch all split sprocket holes. If more than two sprocket 
holes are missing on one side—that is, in succession, of 
course—cut the film and make a splice. Remember, my friend, 
an ounce of prevention is worth a pound of cure. Managers, 
however, should not expect projectionists to inspect films for 
nothing. Such work is no part of his duty and should by ail 
means be paid for, aside from the projectionist’s regular 
salary. 

EMULSION MAY BE REMOVED FROM FILM by soak¬ 
ing the film in warm water, to which ordinary washing soda 
has been added. Put in large double handful of soda to the 
bucket of water. Wash the film afterward in clean, warm 
water. 

CLEANING FILM is a legitimate function of the film ex¬ 
change. Film gradually accumulates more or less dirt and 
oil, all of which is highly injurious to the screen result. 
There are several cleaners on the market, designed for use 
in the projection room. They for the most part consist of an 
arrangement for holding pads of canton flannel or other 
material between which the film is pulled in the process of 
rewinding. These devices remove considerable dust and 
dirt, and at least some of the oil, but have not proven very 
popular, one reason being that there is always the possibility 
of damaging the film badly by some foreign substance stick¬ 
ing on the pads and scratching the emulsion in a straight 
line all the way through the film. 

Alcohol will remove dirt and will not injure the emulsion, 
but it is likely to cause the film to curl very badly, hence it 
is not to be recommended for the cleaning of film. 

The Research Laboratories of the Eastman Kodak Com¬ 
pany is authority for the assertion that film may be cleaned 


MANAGERS AND PROJECTIONISTS 


291 


with commercially pure tetrachloride without damage, pro¬ 
vided the same be allowed to thoroughly evaporate before 
rewinding the film. To do this it is necessary to wind the 
film spirally on a drying drum, which must be about six feet 
in diameter by six or seven feet long for a thousand feet of 
film. The drum should be revolved until the film is thoroughly 
dry. 

WARNING —If the film be cleaned by being pulled through 
a cloth moistened with tetrachloride, and be immediately 
rewound, sufficient of the fluid may, and probably will remain “ 
to attack and seriously injure the film image by bleaching it 
out. 

Film may be cleaned with gasoline, benzine, toluene or 
zylene, but all these are inflammable. 

The Eastman Company says: “The solvent tetrachlorethy- 
lene, made and sold by the Dow Chemical Company, Midland, 
Michigan, is non-inflammable and can be recommended for 
film cleaning. This substance does not attack the film, and is 
sufficiently non-volatile to remain for a short time before 
evaporating, and so has a chance to dissolve out the grease 
from the film before it is wiped off.” 

After using this solvent, however, the Eastman Company 
recommends that, as a precaution, the film be wound on a 
drying drum, as above described. 

There is at least one firm in New York City which makes 
a business of cleaning film. Its process is quite thorough. 
The projectionist who wishes to use the cotton pad method 
can easily construct a device to hold two canton flannel 
pads, each about six inches long, together under some pres¬ 
sure, between which the film may be drawn in the process of 
rewinding. We do not especially recommend it, but it can be 
done. The pad should consist of at least four or five thick¬ 
nesses of cloth—the more the better. It is even possible for 
the projectionist to remove considerable dirt and oil by pull¬ 
ing the film between absorbent cotton cloths held in his 
hands in the process of rewinding. As we said in the first 
place, however, the cleaning of film is a legitimate function 
of the exchange, and we recommend that the projectionist 
confine his efforts to careful handling of the film, to the end 
that no oil and as little dirt as possible be accumulated 
thereon while it is in his possession. 

CLEANING PROJECTOR AFTER A FILM FIRE.— Burn¬ 
ing film leaves a sticky, brown, gummy substance on metal. 
This may be easily dissolved and removed by washing the 


292 


HANDBOOK OF PROJECTION FOR 


metal with ordinary peroxide of hydrogen, which may be 
had at any ten cent store, or at any drug store. 

MEASURING FILM.— All standard professional projec¬ 
tors made in the United States, or, so far as we know, made 
anywhere in the Americas, pass exactly one foot of film to 
each turn of the crank shaft. The number of feet of film in 
a reel may therefore be measured merely by running it 
through one of these projectors and counting the number of 
turns of the crank shaft, which will be equal to the number 
of feet of film passing through the projector. Thus, if while 
running a given subject the crank shaft of the projector 
revolves 980 times, there are just 980 feet of film in that 
subject. 



Figure 80-A. 

There are also several film measuring devices on the mar¬ 
ket, which may be had of any dealer in motion picture 
supplies. 

The way these devices operate is illustrated in Fig. 80-A. 
A very good makeshift film measurer may be had by discon¬ 
necting the intermittent of an old standard projector, using 
only the upper sprocket. One turn of the crank is then 
equal to one foot of film. 





MANAGERS AND PROJECTIONISTS 


293 


The Projection Room 

T HE projection room may properly be described as the 
heart of the motion picture theatre, since from it 
comes at least the major portion, and in some cases 
all of the entertainment provided by the theatre. 

In the beginning of the industry the practice was to house 
the projector in a more or less flimsy enclosure, of the small¬ 
est possible dimensions, unventilated and located anywhere 
space could be found which had no possible value for any 
other purpose. 

Of late, however, thanks at least in some measure to the 
work of the handbook and the projection department of 
Moving Picture World, exhibitors are beginning to under¬ 
stand something of the importance of a well constructed, 
commodious, well ventilated projection room; also that un¬ 
less the same be so located that the projection lens will be 
central with the center of the screen, distortion of the 
picture and other evils will inevitably result; see Page 253. 

LOCATION. —As has been explained under “Keystone 
Effect,” Page 253, a location of the projection room which 
will produce a heavy angle of projection will not only result 
in distortion of the picture outline, but also of everything 
within the picture itself, and while it is possible to correct 
the outline distortion insofar as has to do with making the 
sides of the picture parallel, the distortion of objects in the 
picture itself can only be remedied by changing the angle of 
projection, which in practice means changing the location of 
the projection room. 

In considering this matter the exhibitor and projectionist 
should understand that it is the angle which counts. This 
means that distance of lens from screen is a big factor in the 
matter, as is shown in Fig. 75, in which the height of center 
of projection lens above center of screen is the same in all 
cases. The 40-foot distance gives a 32 degree angle, the 80- 
foot distance only an 11 degree angle, while if the lens be 
moved back to 120 feet the angle would be only 7 degrees. 
This teaches us that if the projection distance be short, it is 
necessary, if the distortion is to be confined within a given 
permissible limit, that the height of the projection lens above 


294 HANDBOOK OF PROJECTION FOR 

the screen center be much less than if the projection distance 
be long. 

The Society of Motion Picture Engineers has set its seal 
of approval on the following: 

“PROJECTION ANGLE. —The maximum permissible 
angle of projection shall not exceed twelve degrees (12°) 
from a perpendicular to the screen surface.” 

While this is somewhat ambiguous, we may, we think, 
accept it as meaning that the maximum permissible angle of 
projection shall not exceed twelve (12) degrees from a hori¬ 
zontal line passing through the center of the screen, when 
the screen sets perpendicular. 

An angle of 12 degrees amounts, roughly, to 2.55 inches 
to the foot. By “roughly” we mean that is close enough for 
practical purposes, though it may be a very small fraction 
of an inch more or less. From the foregoing we readily see 
that if we 

Multiply the proposed projection distance, in feet, by 2.55 
and divide the result thus obtained by 12, the final result will 
be the height, in feet, the lens may be above the screen cen¬ 
ter without exceeding a 12 degree angle of projection. 

By subtracting the distance of the projection lens from 
the floor of the projection room from the result obtained by 
the application of the above rule we shall have the maximum 
permissible height of the projection room floor above the 
screen center. See remarks concerning 12 degree angle. Page 
255. 

In considering possible available projection room locations 
the angle of projection, and consequent distortion are, of 
course, of first importance, though this consideration is 
rivaled by another, namely, 

LIMITS OF VIEW. —Select any familiar object, such as, 
for instance, a tree. Carefully observe it, in normal light, at 
a distance of 150 feet. You will of course see the tree as a 
whole quite plainly. You may even see most of its individual 
leaves, though in some places, unless your eyes are above 
the average, they will appear mostly as green masses of 
foliage, with the outline of individual leaves difficult to trace. 
Advance to a one hundred foot distance. You can now per¬ 
haps distinguish the outline of all the leaves, but the trunk 
most likely will only show as a light or dark object, without 
much detail of the bark being visible. Advance to seventy- 
five feet and see how much more clearly you are able to 


MANAGERS AND PROJECTIONISTS 


295 


distinguish the individual leaves, and how the detail of the 
bark begins to show. 

Precisely the same thing which was true of the tree is 
true of the picture on the screen as observed by the projec¬ 
tionist only, due to difficulty of looking through a compara¬ 
tively small opening in the wall of an all too often well 
lighted room, the detail of the foliage of the actual tree will 
appear much more clearly than will the detail of the image 
of the same thing on a screen, distance being equal. 

It therefore follows that distance of screen from projec¬ 
tion room is of vital importance, since if the distance be 
too great the projectionist will not have a clear view of the 
detail of the picture, hence will be unable to judge of the 
fine sharpness of focus, and sharpness of focus is of vital 
importance, since it has intimately to do with eye strain. 

Many exhibitors permit the establishing of an abnormally 
long projection distance, and then try to compensate for the 
poor view the projectionist has of his screen by providing 
an opera glass. This latter is, of course, an excellent thing 
to do, even with a short projection distance, because there 
are times when the projectionist will wish to observe the 
screen very closely, but to attempt to compensate for a too- 
long projection distance thus is in the nature of a makeshift, 
and one which is only partly successful, because a projec¬ 
tionist just simply will not use a glass as often as would be 
necessary for the best possible results. 

It is just plain common sense that the picture should be 
kept in as sharp focus or definition as possible. 

It is also just plain common sense that if the projection 
room is so far from the screen that the projectionist cannot 
see the finer details of his picture clearly and sharply, the 
picture will not be in constant sharp focus, or at least not 
in the sharpest possible focus. 

Oh yes, we grant you the projectionist can use an opera 
glass, but, as we before said, he won’t, at least not with 
sufficient regularity to insure 100 per cent, sharpness. 

It therefore follows that for best results (and any other 
than best results will inevitably react to the injury of box 
office receipts) the projection room must not be placed too 
far from the screen. But to determine the maximum per¬ 
missible limit of distance is a difficult matter. Perhaps it 
may be best disposed of by saying that beyond seventy-five 
feet the view of the picture from the projection room can- 


296 


HANDBOOK OF PROJECTION FOR 


not possibly be what it should and must be for best results, 
hence the result will inevitably suffer at least to some ex¬ 
tent, insofar as concerns sharpness of focus. Of course as 
the distance increases the view of the screen from the pro¬ 
jection room will become less distinct. 

But this element interlocks with another to the extent 
that any distance sufficiently short to require a projection 
lens of very short focal length—say less than 4 inch E-F, 
is highly objectionable, because very short focal length 
lenses do not give sharpness of definition all over the field. 

The whole subject of projection room location is full of 
complications, but it may be set down as fact that, except 
in those few cases where extraordinary sacrifice would have 
to be made to do it, it will be a paying proposition to so 
locate the projection room that the picture height will not 
be increased by more than 5 per cent, through distortion 
due to angle of projection, and the projection distance 
(throw) such that not less than a 4-inch E-F projection 
lens will be required and as little more than seventy-five 
feet from lens to screen as can be accomplished. 

FRONT OF BALCONY LOCATION.— The location which 
promises best results in large theatres is in the body of the 
balcony. This location is a recognized possibility by some 
architects now, and will, we have faith to believe, become 
increasingly popular when theatres are planned in which 
there is to be a balcony, and in which other available loca¬ 
tions would either give a too steep projection pitch, or else 
a too great distance of projection. 

In Fig. 81 we see the diagrammatic representation of the 
possibility of such a location. The possible objections are: 
(a) Cost of installation, (b) That the balcony will sag 
somewhat under stress of load, (c) That proper ventila¬ 
tion will be difficult, (d) That in case of fire there would 
be danger of panic by reason of smoke coming out in the 
midst of the audience. 

These objections are, except for the first named, capable 
of being reduced to practically nothing at all. The balcony 
will settle somewhat, yes, but it is a simple matter to con¬ 
struct a compensating projector table which will take care 
of this and keep the picture automatically centered on the 
screen. See Fig. 81 A. Such a room may be ventilated as 
much as may be desired. It is merely a matter of cost of 
necessary vent ducts, and their installation; also ducts may 
be easily provided which will carry away every particle of 


MANAGERS AND PROJECTIONISTS 


297 



Figure 81. 










































































































































































298 HANDBOOK OF PROJECTION FOR 

smoke and gas in case of fire, so that although a portion of 
the audience may, and probably will, be seated literally 
within eighteen inches of the ceiling of the room, they will 
not be aware of anything more than a stoppage of the show 
should a fire occur. It is a simple problem to make such a 
room practically entirely sound proof. In fact, there is no 
valid objection to such a projection room location, except 
the matter of installation cost. It is a lamentable fact that 

both architects 
and exhibitors, 
with some excep¬ 
tions, seem im¬ 
bued with the 
idea that projec¬ 
tion room loca¬ 
tion is of no par¬ 
ticular import¬ 
ance. This error 
•is tremendously 
harmful to the in¬ 
dustry, because it 
makes for inferior 
results on the 
screen, and in¬ 
ferior results on the screen make for a less pleasing general 
screen result, with consequent lessened patronage. 

THE MAIN FLOOR LOCATION.— The location of the 
projection room on the main floor of the auditorium offers 
no insuperable, or even largely objectionable difficulties, as 
has been amply proven in the west, where many high-class 
theatres have projection rooms thus installed. It is very 
largely a matter of occupying space which might otherwise 
be devoted to high-priced seats. 

The point the exhibitor who objects to the main floor 1 
location overlooks, is that with a main floor projection 
room location he gets maximum possibility for screen re¬ 
sults, hence greater drawing power at his box office. 

Take a theatre seating two thousand, for example. As¬ 
sume it to give three shows a day. It then has 2,000x3*= 
6,000 seats to sell each day. Suppose the projection room 
occupies space in which 30 seats might be placed, and that 
those seats, if filled, will sell for fifty cents each, or forty- 
five dollars a day. Mark you well the IF FILLED. Holw 
many theatres do sell their entire seating capacity for thrie 
shows? Very few, if any, except in the case of attractions 



Figure 81 A. 








MANAGERS AND PROJECTIONISTS 


299 


which have within themselves an extraordinary drawing 
power, hence we may reduce the loss by at least one-third, 
making it thirty dollars. But even that is a very serious 
matter, unless compensated for. 

And right there, Mr. Exhibitor, we ask you to think very 
carefully. You will, we believe, agree that a clear cut, un¬ 
distorted picture will be more pleasing to your audiences 
than will the heavily distorted picture which is not in the 
sharpest possible focus (two faults which are the invariable 
accompaniment of the long projection distance and the top 
of the balcony projection room location) and that the more 
pleasing picture, or more pleasing general screen result 
must and will operate to the benefit of the box office. Is it 
not therefore reasonable to suppose that by the sacrifice of 
some of your high-priced orchestra seats (which will only 
be really sacrificed when you have a capacity house) you 
will sell a greater number of seats at times when your 
theatre is not normally full. In other words, while the per¬ 
fect screen result cannot increase the business of your 
capacity shows, it can and will increase the business at the 
shows which do not do a capacity business. 

The fact is that the perfect screen result upon a main 
floor location will sell more than enough additional seats to 
make up for those lost, while the front-of-balcony location 
will sell the additional seats without entailing any sacrifice 
in seating capacity. 

One objection advanced as against the main floor location 
is that it necessarily restricts the size of the projection 
room. True, but immediately below usually is plenty of 
available room in the basement, in which re-winding can be 
done, repairs made and where motor generators, etc., can be 
located, the room below being connected with the projec¬ 
tion room by an incline or a stair. 

The main floor location is of course usually only available 
in theatres planned to accommodate it, because the meth¬ 
ods for disposing of smoke and gas must be taken care of 
in the structure of the house. Otherwise it would be diffi¬ 
cult, if not impossible, to install the necessary ducts without 
sadly marring the beauty of the theatre. 

Summed up, the rear of the auditorium at the top of the 
balcony is usually a miserable projection room location, 
from the viewpoint of excellence in screen results. It gen¬ 
erally gives projection pitch far in excess of that permis¬ 
sible in good practice. It usually gives a too-long projec¬ 
tion distance, which operates to produce heavy waste of 


300 


HANDBOOK OF PROJECTION FOR 


light in the projector optical system, as well as to make im¬ 
practical the maintenance of maximum sharpness in focus 
of the picture. The only advantages of such a location are 
ease of ventilation, ease of taking care of smoke in case of 
fire, ease of sound-proofing and cheapness of installation. 
In other words it barters high-class screen results for 
cheapness of installation and ease of operation. 

The front-of-balcony location costs more to install, but 
should give an almost ideal projection distance. If properly 
installed its fire dangers are purely imaginary, its thorough 
ventilation entirely practical and it may be depended upon 
to provide a projection angle well within the permissible 
limit. Special projector tables, Fig. 81 A, will automatically 
take care of displacement of picture through sag of balcony 
under load. 

The main floor location is entirely practical, from any and 
every viewpoint. Its only legitimate objection is that it is 
more costly of installation, and reduces seating capacity, 
though in the long run it may be depended upon to produce 
quite sufficient revenue to more than compensate for the 
seating space it occupies. 

The following may be considered as the essentials of a 
first-class up-to-date projection room: 

(A) It must be so located that a point central between 
the two projector lens ports will be exactly centered with 
the center of the screen sidewise, and its height above the 
center of the screen must be such that the distortion of the 
picture will in no cases exceed 5 per cent, of its normal or 
undistorted height. 

(B) The minimum distance of the projectors from the 
screen should be such as will call for the use of a projection 
lens of not less than 4-inch E-F. Anything less than this 
focal length will make it either very difficult, or impossible 
to secure sharp definition all over the screen without reduc¬ 
ing the working opening of the projection lens, which 
means loss of light. On the other hand the distance from 
the lens to the screen may be as much as 250, or even 300 
feet, though we would advise against such an attempt and 
very strongly recommend that the projection distance be 
kept within a maximum of 75 or at most 100 feet, since long 
projection distance means loss of light in the optical system 
and more or less tendency to lack of sharpness in the pic¬ 
ture through inability of the projectionist to see it clearly. 

(C) The projection room must be absolutely fireproof, 


MANAGERS AND PROJECTIONISTS 


301 


which includes not only the construction of the room itself, 
but the shuttering of its ports and the providing of suffi¬ 
cient vent pipe area to carry away all the smoke and fumes 
of burning film. 

(D) The projection room must have a very solid founda¬ 
tion, since the least vibration in the floor will inevitably 
produce vibration of the picture upon the screen. 

(E) The projection room must be as nearly as possible 
soundproof, to the end that the noise of the projectors, the 
rewinder, and the motor generator set or transformer, as 
well as the conversation sometimes necessary between the 
projectionist and his assistant be not audible in the audi¬ 
torium. 

(F) The lighting of the projection room must be such 
that in case of trouble the room may be instantly and bril¬ 
liantly illuminated, to the end that repairs proceed with 
maximum speed. The lighting must, however, be so ar¬ 
ranged that the projectionist may either extinguish all 
lights, or else greatly dim the illumination by means of a 
switch located within convenient reach from his position be¬ 
side either one of the projectors. 

(G) The color of the walls and ceiling is important. The 
optically correct color for the interior of projection rooms 
is a non-gloss dead black, but where this is objected to a 
very dark bronze green or a dark brown or chocolate may 
be substituted with satisfactory results.. The important 
thing is that the best possible view of the screen is had 
when the projection room is dark, and the darker it is the 
better will be the view of the screen. 

(H) The projection room should be reasonably easy of 
access, preferably not opening directly into the auditorium. 
It should be reached by a stairway rather than by a ladder. 
If it does open directly into the auditorium, then the stair¬ 
way or ladder should be surrounded by some sort of par¬ 
tition so that in case of fire the projectionist may leave the 
room without allowing a cloud of smoke to escape into the 
auditorium to terrify the audience. 

(I) The projection room should be large enough for rea¬ 
sonable comfort, allowing not less than two feet in the 
clear behind the projectors, after they have been set far 
enough back from the front wall, so that the projectionist 
may pass between the lens and the wall, with not less than 
six feet in width for a single projector and 3 feet additional 
for each additional projector, stereopticon or spot light. 


302 


HANDBOOK OF PROJECTION FOR 


The ceiling should be as high as practicable—the higher the 
better, within reason of course. In any event 78 inches from 
floor to ceiling should be the absolute minimum. 

(J) All openings must be equipped with fireproof shut¬ 
ters or doors which will close quickly and automatically in 
case of fire, except the vent flue, which must be unobstruct¬ 
ed if there is a fan; if of the open type then it must have a 
damper weighted to remain normally open, as will be here¬ 
inafter explained. 

(K) There must be a» vent flue or flues leading preferably 
as nearly as possible directly to the open air above the 
roof. 

(L) All wires must be in conduit, and the conduit system 
must be thoroughly grounded. Fuses and switches should 
be in metal cabinets or cabinets built into the wall and cov¬ 
ered with a metal facing, except in cases where a regular 
switchboard is employed. Conduits should, where possible, 
be built into the walls, and conduits leading to the pro¬ 
jectors should be carried under the floor to a point immedi¬ 
ately beneath the lamp house of each projector. 

(M) The projection room must contain nothing except 
those things necessary to the work of proiection. 

(N) There should be proper tool racks, and a separate 
closet for each projectionist’s clothes and tools ; also either 
in the projection room or immediately adjacent thereto 
should be a substantial work bench equipped with a sub¬ 
stantial metal vise and a small anvil, which two last named 
may be combined in one. 

The switches and apparatus should be so arranged that 
they will be easy of access to the projectionist, both for 
manipulation and for repair. Making things unhandy for 
the projectionist is one of the most expensive things we 
know of. 

(P) It should contain only the most up-to-date apparatus, 
which same must be kept in the best possible condition. 

(Q) The projection room must have observation ports of 
such size that the projectionist may have a clear, unob¬ 
structed view of the entire screen, either when seated or 
standing in working position beside his projector. 

(R) The exterior of the room should be as inconspicuous 
as possible; that is to say, it should be decorated to har¬ 
monize with the rest of the theatre if it projects into or oc¬ 
cupies a position in the main auditorium. 


MANAGERS AND PROJECTIONISTS 


303 


(S) If good results are to be expected and those results 
are to be had with a maximum of efficiency, the projection 
room must be placed in charge of a thoroughly competent 
reliable staff of projectionists, who are possessed of both 
practical and technical knowledge of the art of projection, 
and who are able to supplement their knowledge by a good 
fund of borse sense. No applications for position as pro¬ 
jectionist should be considered unless the applicant can 
show that he has served at least one year’s bonafide appren¬ 
ticeship in a projection room. 

(T) Either in the projection room or immediately adja¬ 
cent thereto should be a wash bowl with running water. In 
handling carbons and in oiling the projectionist gets more 
or less grime on his hands, and unless this be washed off 
some of it will adhere to the films, to their damage. It is 
also imperatively necessary that toilet facilities be provided. 

(U) There should be a telephone to the manager’s office 
and, under some conditions, to the orchestra pit and stage. 
This is essential to modern practice. It should be a house 
phone only, not connecting with outside telephones, though 
an arrangement may well be made for such connection, but 
through the manager’s office only. 

(V) Proper tanks must be provided for storage of films 
when not in use. These tanks should be such as will (a) 
provide a separate fireproof compartment for each reel, 
(b) Each compartment should close automatically by grav¬ 
ity. (c) Top of tank should be so shaped that it will not 
serve as a shelf for reels of film or other things, (d) Place 
should be provided for moisture-containing sponge. 

(W) In case the houselights are not handled from the 
projection room, there should always be a switch therein 
by means of which the projectionist will be enabled to light 
the auditorium instantly in case of serious trouble. 

The foregoing constitutes what might be termed the fun¬ 
damental essentials of projection room construction and 
equipment, but in addition a detailed explanation of the 
various things is necessary. 

PROJECTION ROOM DOOR— The door of the projec¬ 
tion room must not be less than two feet wide by six feet 
in height. It must, of course, be built of fireproof material. 
Three-eighths inch asbestos mill board on both sides of a 
steel frame is perhaps best. The door may be either hung 
on hinges, in which case it must always open outward and 
be held normally closed by a substantial spring, or, very 


304 


HANDBOOK OF PROJECTION FOR 


much better, it may be a sliding door so arranged that it 
will be normally held shut by gravity. 

This latter idea is illustrated in Fig. 82, in which is a door 
constructed as above set forth, hung on an inclined track. 
Such a door is easy of manipulation and not expensive in 
first cost. It will always remain closed unless it be deliber¬ 
ately fastened open. 



THE FLOOR. —The foundation for the projection room 
floor will, of course, vary with the circumstances of the in¬ 
stallation, but it must be such as will hold a floor absolutely 
without movement or vibration of any kind, because if the 
projection room floor moves or vibrates, then the projector 
itself will move and vibrate, which means that the picture 
on the screen will move or vibrate, and this latter may be a 
very serious matter, indeed. 

Suppose the projection room floor to vibrate evenly all 
over precisely 1/16 of an inch. This would mean that the 
whole picture would move up and down on the screen exact¬ 
ly that much, which would, if the vibration was only occa¬ 
sional, probably be imperceptible, but would, if the vibra¬ 
tion be rapid, have the effect of injuring the definition of 
the picture. But suppose the floor vibrate in such manner 








MANAGERS AND PROJECTIONISTS 


305 


that the condenser be moved up and down 1 /64th of an inch 
more than the projection lens. This would set up a condi¬ 
tion such as is shown in Fig. 83 and the effect on the picture 
on the screen would increase in proportion as the distance 
from the lens to the screen increases. In Fig. 83 A is the 
light source and B the projection lens. If A be moved 
down l/64th of an inch, B remaining stationary you will 
readily see that the movement of the light beam at a point 
say 100 feet away will be considerable. The dotted line 
illustrates the result. 

Modern practice is to provide a solid foundation upon 
which is placed not less than six inches of a rich concrete, 
well tamped down. On this is placed a top dressing of 

^- & . .- — 7-- — 

Figure 83. 

cement from .5 of an inch to one inch thick, essentially of 
the same composition as is used for side walks. 

WARNING.—An enormous amount of damage is done 
both to machinery and to film by improper mixing of the 
top dressing of projection room floors, or by the use of poor 
cements. If the top dressing be not properly mixed, or if it 
be of poor material, it will constantly wear off, and the re¬ 
sultant dust is a very fine abrasive powder. It gets into the 
bearings of projectors, motors and generators and wears 
them out very rapidly. It gets on the film and is one of the 
greatest rain producers known. We have seen many pro¬ 
jection rooms in which an improper top floor dressing was 
shortening the life of the machinery enormously, as well as 
doing immense damage to the films used therein. 

FLOOR DRESSING. —Where such a floor exists it is pos¬ 
sible to apply a preparation which will stop the trouble, or 
the floor may be painted with a good floor paint. Exhibit¬ 
ors will do well to remember that a projection room cement 
floor which slowly disintegrates into dust is about as great 
a damage producer as they can have in their theatre, and 
one great trouble with this particular thing is that the dam¬ 
age done is so nearly imperceptible that neither the ex¬ 
hibitor or the projectionist realizes how serious it really is. 

One of the best possible coverings for a projection room 
floor is a heavy matting made of a cork composition, such 




306 


HANDBOOK OF PROJECTION FOR 


as battleship linoleum, but the plain cement finish will not 
produce trouble if it is made from a proper mixture of good 
cement. A floor built of concrete as described, finished with 
a proper top dressing of cement, will to all intents and pur¬ 
poses be just one solid block of stone, and you will have no 
vibration at all, because a thing of that kind is altogether 
too heavy to vibrate. 

WALL CONSTRUCTION.— Where there is no objection 
to weight, cement or brick is very good for wall construc¬ 
tion. Either is, of course, thoroughly fireproof. Hollow tile 
has distinct advantages, however. If properly and carefully 
laid in rich mortar, well tempered with cement, it is just as 
good for the purpose, viewed merely as a wall, as cement 
or brick, and is much more nearly soundproof than either; 
also it does not act as a heat reservoir as does brick and 
cement. Where hollow tile is used it should be well plastered 
on both sides, either with one of the hard-setting patent 
plasters, or with a strong lime mortar strongly tempered 
with cement. 

When either of the three before named forms of con¬ 
struction are used the ceiling may be of the same material, 
carried in the usual way, between I beams. 

It is not the purpose of this work to enter into details of 
construction. That is the business of the architect. Our 
intent is only to point out those things which practice has 
proven to be satisfactory. 

BUILDING IN CONDUIT. —All projection room circuits 
must be in conduit, and where cement construction is used 
it is much better that the conduit be placed in position as 
the walls are built, so that it will be imbedded in the walls 
themselves. Where brick construction is used it is possible 
to leave grooves in the wall, so that the conduit can be 
placed therein and afterward imbedded in plaster. The 
bricklayer mason may charge extra on account of the 
trouble involved in doing this, but it nevertheless is prac¬ 
tical and worth while, because the conduit is then not only 
held firmly in place, but becomes a part of the wall itself. 

PORTS. —Each projector must be provided with a lens 
port and one observation port. Each stereopticon must 
have one observation and one lens port, but a spot light 
need only be provided with one large port. Of course if the 
projector be provided with a stereopticon attachment, then 
a separate port must be provided for slide projection. 


MANAGERS AND PROJECTIONISTS 


307 


LOCATING PORTS. —The way architects locate lens and 
observation ports usually results in handicapping projection 
forever after. The average architects, if we are to judge by 
what they do, have little, if any, comprehension of the im¬ 
portance of properly located ports of proper size. They 
locate a lens port somewhere near right, and an observation 
port which, four times out of five, is nothing short of an 
outrage, and which makes high class screen results highly 
improbable, if not entirely impossible. We strongly recom¬ 
mend the following procedure in planning the projection 
room front wall. 

Lay out the openings as per Fig. 84, in which A and B are 



Figure 84. 


the projector lens ports, C and D the projector observation 
ports, E and F respectively the stereopticon lens and obser¬ 
vation ports, the latter of which may be made any size 
desired not less than ten inches square. 

It will be noted that the projector lens ports are indicated 
as twelve inches square. This is for the reasons given fur¬ 
ther along. If it is not desired to follow the procedure we 
shall indicate for filling in the lens ports, then their size may 
be reduced accordingly, but the filling-in plan is most satis¬ 
factory in the end. 

The distance between ports A and B is the absolute mini¬ 
mum consistent with good work and decent conditions. It 
should never be less, and should never be more where the 
distance of projection and picture size be such that a pro¬ 
jection lens of less than 6-inch E-F is required. When the 
projection lens E-F exceeds 6 inches, the distance between 
ports A and B may be increased gradually as the E-F of 













































308 


HANDBOOK OF PROJECTION FOR 


required lenses increases, until with an 8-inch E-F lens it 
is possible to have as much as five feet between projector 
lens centers, though four feet gives ample room and should 
not be exceeded. 

The distance between stereopticon and spot may be re¬ 
duced, if necessary, as may also the distance between the 
stereopticon and left hand projector, though we do not 
advise this latter if it can in any way be avoided, as it sets 
up a bad condition. 

Ports A and B must, of course, be spaced equi-distant 
from the center line of the screen. 

The distance from port B to the wall also is intended as 
an absolute minimum. It is, in fact, too little. When it is 
possible, at least, another foot should be allowed. 

CAUTION.— The distance of the center of projector ob¬ 
servation ports C and D above the floor is shown as 60 
inches, which is about right, everything considered, for 
level projection and the average man, but if there is consid¬ 
erable pitch in the projection the ports will be too high. It 
will be found very satisfactory to make the projector ob¬ 
servation ports 16 inches wide, with their centers 60 inches 
from the floor, and then lower them four and one-quarter 
(4.25) inches for every five degrees pitch in the projection. 

•Thus: If there be a 20 degree pitch in projection, then 
the centers of the sixteen-inch-square observation ports 
should be (4.25x4=17) 60—17=43 inches from the floor. If 
there is considerable pitch in projection it will also be 
necessary to lower the lens ports. 

It will be observed that ports A and B are 16 inches 
square, and that port E is 18 inches high by 8 inches wide, 
which is, of course, far in excess of the actual requirement. 
The center of the lens of the average projector is about 48 
inches from the floor when the projector is level. The idea 
in making the lens port opening of the wall 12 inches square 
is that after the projectors are placed in position and the 
light properly centered on the screen the opening may be 
filled in as per Fig. 85, in which A is an asbestos mill board 
inch thick set into the opening and flush with the outside 
edge of the wall. This is only placed in the port after pro¬ 
jector has been set in place and the light has been centered 
on the screen. After placing board A in position, turn on 
the light, which will form a spot on board A. With a 
pencil, mark around the outer edge of the spot and then 
cut a hole in the board just a bit larger. Next a similar 


MANAGERS AND PROJECTIONISTS 


309 


board is placed as per C and the hole marked in the same 
way and cut out, after which the two boards are placed in 
position and bolted together, a wood spacer being used as 
shown. We thus have a lens port exactly the size of the 
requirements of the local condition. F-F are bolts holding 
the whole thing together. This port filling is effective and 
its cost is small. Stereopticon lens port E should be filled 

in in the same way. 
Flanges of asbestos 
mill board may be 
added, as per dotted 
lines, if desired. 

C and D, Fig. 84, 
are, you will ob¬ 
serve, 16 x 16 inches 
in dimension, with 
their horizontal cen- 
t e r s located 60 
inches from the 
floor line, and the 
vertical center 18 
inches from the cen¬ 
ters of the lens 
ports. Observation 
ports should, under 
no circumstances, be 
less than 12 inches 
wide, and 16 is much 
better. Anything less 
than 12 inches com¬ 
pels the projection¬ 
ist to put his eyes 
right up against the 
port in order to get a 
clear view of the 
screen. The average 
layman, or even the 
average projection¬ 
ist, does not realize how true this is, or what an effect the 
narrow observation port has in injury to the definition of the 
picture on the screen, by reason of the fact that the projec¬ 
tionist just simply cannot see clearly through a small hole. 
Where a local law limits the size of observation ports it is 
entirely practical to cover a large port with a sliding shutter 
in which an opening 12 inches wide by 6 or 8 inches high has 


















310 


HANDBOOK OF PROJECTION FOR 


been cut. This sliding shutter must be so arranged that 
the bottom of the opening in it may come down to the 
bottom, and the top of the opening raise to the top of the 
hole in the wall. It should be arranged with a counter¬ 
weight so that the projectionist may move the opening up 
or down to the most convenient position. The plan is illus¬ 
trated in Fig. 86. 



Figure 86. 


The important point in making an observation port of 
generous size is that unless the projectionist watches his 
screen constantly there will be faults of various kinds in 
the projection, and most certainly there will be little if 
any of that regulation of the speed of projection which is 
so necessary to high class work. Moreover, unless the port 
be of ample size, the definition of the picture on the screen 
will not be as sharp as it should be, which means added 
and unnecessary eye strain to the patrons of the theatre. 

GLASS OVER PORTS.— It is entirely practical to place 
glass over the observation ports, provided the right kind of 
glass be used, and further provided the glass be properly 
installed and KEPT CLEAN. An old photographic plate 
with the emulsion cleaned off is the best glass to use, though 





























MANAGERS AND PROJECTIONISTS 311 

any high grade glass will do. See Page 290 for directions 
for removing photographic emulsion. 

Where glass is placed in an observation port it should be 
set at an angle from the vertical, which will serve to kill 
the reflection from its polished surface. It must either be 
made easily removable, or be hung on hinges so that it may 
be readily cleaned on its outer surface. If the glass be set 
at an angle, and the port be surrounded by a shadow box 
painted black on the inside, as per Fig. 87, the reflection 

from the glass will be en¬ 
tirely killed and the view 
of the screen made very 
much better. 

In one of the San Diego, 
California theatres the 
author saw what seemed 
to be the ideal observation 
port. It was located be¬ 
tween the projectors, was 
about 30 inches square and 
was covered with plate 
glass, ill the center of 
which a circle 10 inches in 
diameter had been cut out. 
With such a port it seems 
possible to have the pro¬ 
jection room at all times 
fairly well lighted, pro¬ 
vided the lights be prop¬ 
erly placed, and at the 
same time to have a most 
excellent view of the 
screen. 

GLASS IN LENS PORTS. —Many projectionists now use 
glass in both the lens and observation ports. The glass 
over the lens port need not necessarily do any harm, insofar 
as the definition of the picture be concerned, but it does 
cause considerable loss through reflection, particularly if 
it is not kept scrupulously clean. If the lens port be re¬ 
duced to the actual requirement of the beam there is seldom 
any necessity for covering it with glass, since the opening 
will be very small. Our advice is to reduce the lens ports 
to the actual requirement, as per Page 309, and omit the 
glass. 



Figure 87. 







312 


HANDBOOK OF PROJECTION FOR 


SMALL PORTS AND THE LAW.— In some states the 
size of projection room ports is limited by law, and the 
limitation is such that high class projection is prevented, 
since it is impossible for the projectionist to secure a really 
good view of his screen, even when right up against the 
port. 

WE CHALLENGE ALL SUCH LIMITATIONS AS 
SERVING ABSOLUTELY NO GOOD PURPOSE, EITHER 
IN SAFETY OR ANYTHING ELSE. 

In case of fire, smoke will make its way through a small 
opening practically just as quickly as it will through a large 
one, and if the audience once gets sight of smoke the 
damage is done and the panic started, if there is going to 
be one. The escape of smoke from the projection room is, 
however, supposed to be prevented by the fire shutters and 
there will not be the difference of l/25th of a second in 
the time required for a shutter to drop over an opening 16 
inches square and the time required for a shutter to drop 
over an opening 4 inches wide by 12 inches high. 

Then, too, the larger shutter being much heavier is less 
likely to stick than the small one, which actually places the 
balance on the side of the large opening, insofar as con¬ 
cerns safety. 

If law makers and inspectors would pay more attention 
to the proper construction of port shutters and the proper 
placing of the fuses in the lines which support them, leaving 
the size of the opening to take care of itself, the result, in¬ 
sofar as concerns the safety of the public, would be greatly 
improved, and the enormous handicap against projection 
caused by small observation ports would be removed, to the 
great benefit of results on the screen, the lessening of eye 
strain for the spectators and the increasing of the enjoy¬ 
ment of the show by the public. 

SPOT LIGHT PORT. —The spot light port, if one there 
be, should be located with its center about 4 feet 6 inches 
above the floor line. The opening should be 16 to 18 inches 
in diameter, square or round, as preferred. 

PORT FIRE SHUTTERS. —Every observation port, lens 
port and spot light port should be provided with a fire 
shutter. The best material from which to make these 
shutters is asbestos mill board, of an inch thick. Some 
authorities are satisfied with 16-gauge sheet metal, which 
will serve very well, though it is not, we believe, all things 


MANAGERS AND PROJECTIONISTS 313 

considered, as satisfactory for the purpose as asbestos 
board. 

The proper installation of port shutters, together with an 
adequate vent flue and thoroughly fireproof walls offer not 
only adequate protection from fire damage to anything out¬ 
side the projection room, but also against the probability of 
alarm on the part of the spectators should a fire occur in 
the projection room. This latter desirable end will, how¬ 
ever, not be accomplished unless the port shutters be so 
hung that they will close the instant fire starts. This is of 
absolutely supreme importance. It is very, very seldom, if 
ever, that a projection room fire does any injury to any¬ 
thing outside the projection room itself. The damage is 
practically always caused by the panic which almost in¬ 
variably follows an alarm of fire where an audience is 
gathered. Now that all projection rooms are fireproof, it 
may be stated as a fact that, 

Barring panic, there is absolutely no danger of any kind 
whatsoever to an audience or to any individual thereof 
through a projection room fire. 

A splendid result would be accomplished if all theatres 
were required to run a slide reading something like this, 
before each performance, for a period of six months : 

“The projection room of this theatre is thoroughly fire¬ 
proof. In the improbable event of a film fire there is 
absolutely no danger to the audience, as in no possible event 
could anything more than possibly some smoke reach the 
auditorium.” 

The foregoing might possibly be improved as to its word¬ 
ing, and is intended only as a suggestion. 

It is a deplorable fact, however, that a large proportion 
of the average audience becomes raving maniacs the in¬ 
stant there is an alarm of fire. Given a glimpse of fire or 
smoke you may depend upon them to go stark raving mad, 
pile up in a heap and kill each other either through tramp¬ 
ling or suffocation. 

We desire to strongly impress upon architects and ex¬ 
hibitors and public officials the fact that it is entirely prac¬ 
tical and feasible to prevent the audience from having any 
glimpse of either fire or smoke when a film fire occurs. In 
order to accomplish this, however, port shutters must be so 
fused that they will automatically close every opening in 
the projection room within three or four seconds of the time 
a fire starts. 


314 


HANDBOOK OF PROJECTION FOR 


The port fire shutters should be so arranged that they may 
all be dropped by the projectionist with one motion, but 
depending upon him is by no means a safe thing, since the 
projectionist is but human. When the film catches fire he 
is likely to become more or less excited, and one never can 
tell what an excited man will do, or what he won’t do. We 
therefore emphasize the fact that. 

Port shutters should be so fused that they will auto¬ 
matically close all the ports within three or four seconds of 
the starting of a fire at either projector, at the rewind table 
or the film storage can. 

This latter proposition hinges entirely upon the kind and 
location of the fuse links. All shutters should be held by 



one master cord, and that master cord should contain fuse 
links, preferably of film. But whether the fuse links be of 
film, or the regulation metal fuses should NOT be located 
4 or 5 feet from the probable sources of fire, but as 
closely as possible to (a) each projector upper magazine, 
(b) the film storage magazine and (c) the rewind table. If 
metal fuse links are used they should be of the 160 degree 
fuse metal, or the most sensitive fuse metal obtainable. 
One method of using film links is shown in Fig. 88. 

There are several patent port shutter supporting and 
releasing devices made, and they are all of them good, pro¬ 
vided the fuse link be located where it will do real service. 

There is one plan, however, the invention of F. E. Cawley, 
Mason City, Iowa, which is of such general excellence that 


































MANAGERS AND PROJECTIONISTS 


315 


it deserves description. Its chief point is illustrated in 
Fig. 89, in which A is a round shaft hung in suitable bearings 
attached to front wall at suitable height. To it is attached 
lever B, as shown. In shaft A holes about l /& inch in 
diameter are drilled, passing clear through. These holes 
are indicated at G-G-G. There must be one over the center 
of each port opening. To each port shutter a suitable cord 
or wire is attached, at the other end of which is an ordinary 
cotter pin about an inch long. The same purpose would be 



served by a pin, as at D, and a small harness ring. The 
action is as follows: 

Lever B is raised to horizontal position, which must also 
bring holes G-G-G to horizontal position, and a master cord 
is attached to the hook at its end. This cord may be carried 
down to proper position at each projector, also down over 
the film storage tank and the rewinder table, being fused 
with link or metal fuses, or both, at proper places. It ter¬ 
minates in a metal ring designed to be hooked over a head¬ 
less spike just inside the projection room door. 

It will readily be seen that when the master cord is re¬ 
leased, either by a fuse or by removing the ring from the 





316 


HANDBOOK OF PROJECTION FOR 


spike, lever B will fall, and in so doing will rotate rod A 
one-quarter of a turn, so that holes G-G-G will be vertical, 
whereupon pins C will be released (they must fit very 
loosely in the hole) and the shutters will drop of their own 
weight. 

The superiority of this plan is that it combines the great 
advantage of fusing at as many places as may be desired 
(the master cord really need never be disturbed, except in 
case of emergency, as a fire) and the ability to raise or 
lower each shutter entirely independently of every other 
shutter. Also it can easily be made by any competent black¬ 
smith or machinist. The scheme has our hearty commenda¬ 
tion. 

AUTHORITIES IN ERROR. —As a general proposition 
authorities permit or even demand the locating of port 
shutter fuses near the ceiling. Their theory is that since 
heat rises the air at or near the ceiling will become heated 
very quickly. This is true, but where a panic may hinge on 
a matter of two or three seconds the plan is a very bad 
one. It is all right to locate fuses near the ceiling, but 
there must be other fuses near the probable source of fire. 
Fuses are cheap, and it won’t cost much to use a dozen of 
them. On the other hand a fire panic may be very ex¬ 
pensive in human life. 

Let it be clearly understood that in the foregoing it is 
also presumed that a proper arrangement will be made 
whereby the projectionist may himself drop the port shut¬ 
ters, which should be absolutely the first thing he does, 
after dropping the douser or pulling the switch, when a fire 
starts, since the safety or the audience is paramount to 
everything else. 

PADDING THE FIRE SHUTTERS.— When the port 
shutters drop, their bottom edge should rest either on rub¬ 
ber or felt. The most important purpose of the port shutter 
is to prevent the audience from even knowing there is a fire 
in the projection room. If from four to six heavy shutters 
drop with a crash, the effect is to instantly draw the at¬ 
tention of the entire audience directly to the projection 
room. The pad is designed to avoid this very thing. Of 
course in theory the shutters should be dropped gently, but 
when a fire occurs and the shutters drop automatically 
through the burning of a fuse, gravity won’t act very gently, 
and even if the projectionist drops them he has not, under 
the circumstances, time to be very gentle. 


MANAGERS AND PROJECTIONISTS 317 

Fig. 90 indicates a proper method of padding the shut¬ 
ters to prevent a noise when they drop. 

VENTILATION of the projection room serves three pur¬ 
poses, viz.: to provide fresh air to the men working'therein, 
to keep down the temperature and to provide means for 
carrying off all the smoke and gases generated in case of 
film fire. 

The vent flue should, wherever possible, pass directly 
from the projection room ceiling through the roof to the 
open air, its top being not less than 3 feet above the roof 
and protected by a suitable hood to keep the rain from 
beating in. The open vent flue is neither safe nor de¬ 
sirable, because of the fact that under some conditions it is 


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E1 

1 $ 

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~T’ 

£3o~r~ro/l 

■s 

T ~0 /=»/7CAC/rn 

1 

WiTH Y& 

*~erL x 

VCTOAf £-£>C£:. 


Figure 90. 


quite possible, and even probable, that the draft through an 
open vent would be downward instead of upward. This is 
especially true in some locations when the wind is in certain 
directions, as any housewife who has had experience with a 
smoking chimney can testify. 

The laws o.f some cities or states stipulate a certain size 
vent flue for a certain size projection room, and another size 
flue for a different size projection room. This might be 
correct if only the purposes of ventilation were to be 
served, but one of the important offices of the vent flue is 
to prevent panic by carrying off all the smoke and gases, 
and film burning in a small room makes just as much smoke 
and gas as it does in a large one, hence a small room should 
have just as big a flue as a large one. 








318 


HANDBOOK OF PROJECTION FOR 


If the vent flue or pipe be of the open type it should have 
an area of not less than 288 square inches, regardless of 
the size of the room. 

Where a vent flue depending upon a fan for its action is 
used, the fan should not be less than 24 inches in diameter. 
Where fans are used it is an exceedingly good practice to 
install two vent pipes and two fans instead of one, so that 
in case one of the fans gets out of order there will still be 
the second one to fall back on. This may seem like rather 
an expensive precaution, but since the pipe containing the 
additional fan may join the pipe of the other fan, the added 
expense will be largely that of the second fan, and where 
the safety of the audience is concerned expense should not 
be considered. 

It is essential that the vent flue, if made of metal, be 
thoroughly and completely insulated from any inflammable 
substance throughout its entire length, since it is likely to 
get very hot if there is a serious fire in the projection room. 

With proper means provided for the egress of smoke 
and gas, when a film fire occurs, the projection room with 
fireproof walls will be nothing more nor less than a huge 
stove, the draft being inward around the cracks of the port 
shutters and door, and outward through the vent flue; so 
that no smoke or gas will in any event show in the audi¬ 
torium. Hence the audience will never know there is a fire 
in progress, even though their attention be attracted directly 
to the room by the stoppage of the show. 

In addition to the vent flue, there must, for the sake of' 
establishing healthful conditions through proper ventilation, 
be means provided for the ingress of fresh air. The pro¬ 
jection room is often (we might almost say usually) located 
immediately under the roof of the building, and in con¬ 
sequence is, in summer time, very hot with “natural” heat. 
Add to this the heat generated by the powerful arc lamps, 
as well as perhaps one or two rheostats, and you have a 
condition which makes good ventilation absolutely impera¬ 
tive. 

In connection with this it must also be remembered that 
air taken from the auditorium will not be pure air, and 
where the projection room is near the ceiling will be the 
warmest air in the theatre. 

It must also be remembered that if it is taken in through 
the lens and observation ports a draft is created through 
them which blows directly upon the projectionist, a fact 


MANAGERS AND PROJECTIONISTS 


319 


which has sent many men to their death through pneu¬ 
monia brought on by “cooling off” in the draft before an 
observation port after some rapid repair work in an over¬ 
heated room. 

Where the theatre is provided with a ventilation system 
thorough ventilation for the projection room may be had 
by including it in the ventilation scheme. Where there is 
no such ventilation, then there should be inlet air ducts 
from the outer air, these inlet openings to reach the pro¬ 
jection room near the floor line. The Massachusetts law is 
very good in this respect. It reads as follows: 

Projection rooms to be provided with an inlet in each of 
the four sides, said inlets to be 15 inches long and 3 inches 
high, the lower side of the same not to be more than 2^4 
inches above floor level. Said inlets to be covered on the 
inside by a wire net of not greater than %-inch mesh; 
netting to be firmly secured to the asbestos board by means 
of iron strips and screws. In addition to the above there 
shall be an inlet, in the middle of the bottom of the pro¬ 
jection room, if possible; otherwise in the side or rear of 
the projection room, not over 2*4 inches from the floor. 
Said opening to be not less than 160 square inches area 
for a No. 1 projection room, 200 square inches area for a 
No. 2 projection room, and 280 square inches area for a 
No. 3 projection room; connected with the outside air 
through a galvanized iron pipe with a pitch from the 
projection room downward to the outside wall of the 
building. The opening to be covered with a hood, so ar¬ 
ranged as to keep out the storm, and the entrance to the 
projection room to be covered with a heavy grating over 
54-inch wire mesh, if in wall; and arranged with damper 
hinged at the bottom, and rod or chain to hold said damper 
in any position. Mesh and gratings to be securely fastened 
in place, those in the walls to be bolted on as specified for 
the smaller inlets. 

Note—No. 1, No. 2 and No. 3 refer to the size of rooms. 

PROJECTION ROOM EQUIPMENT.— Remembering that 
the box office receipts of a motion picture theatre Jo a very 
great extent depend upon the excellence of results upon 
the screen, the wise exhibitor will bend every effort toward 
the attainment of high class, artistic projection, and will put 
forth everv reasonable endeavor to secure a high class, 
brilliant, flickerless picture, projected at proper speed. It 
may be put forward as a statement of incontrovertible fact 


320 


HANDBOOK OF PROJECTION FOR 


that there is small probability of continuous high class 
screen results coming from an ill-placed, small, poorly ven¬ 
tilated projection room, poorly equipped with facilities and 
tools, and having inferior or badly worn equipment under 
the charge of a projectionist of mediocre ability. No one 
will, we think, dispute the proposition that the above com¬ 
bination would react seriously upon box office receipts. 

We believe everyone will agree that the best results will 
be had from a properly located, commodious, well ventilated 
projection room, equipped with up-to-date projection 
machinery which is kept in good state of repair, and with 
ample tools and facilities; the whole being in charge of a 
thoroughly competent projectionist; the term “competency” 
including industry and careful attention to detail, as well as 
knowledge. 

In this connection it is well to bear in mind the fact that 

the mere possession of knowledge counts for very little 
if its possessor is too lazy or too shiftless to apply it in 
practice. 

CLOSETS. —In planning the projection room the architect 
should include sufficient cabinets, or closets, with substantial 
locks thereon, so that each individual projectionist may have 
a place to keep his private belongings, including tools. 
The projectionist should have a full equipment of tools, but 
it is rather discouraging to provide them and then be com¬ 
pelled to leave them at the mercy of anyone, from the 
janitor to a chance visitor, to say nothing of the other pro¬ 
jectionist who perhaps has none of his own, and moreover 
may not be inclined to take the best care of those belonging 
to others. 

There should also be drawers, or a closet in which to keep 
supplies, such as carbons, extra lenses, etcetera, though, of 
course, a shelf will do, and if the walls be built of cement 
it is a comparatively simple matter to provide cement 
shelves when the room is constructed. There should also be 
plenty of hooks on which to hang spare wire, etcetera. It 
is an exceedingly unprofitable thing to spend time hunting 
for a piece of wire, a tool or some needed repair part when 
something goes wrong. 

It is of the utmost importance to orderly procedure and 
rapid work in a projection room that things be kept in 
their place, but in order to keep things in their place it is 
necessary to have a place to keep them in, and that is some- 


MANAGERS AND PROJECTIONISTS 


321 


thing it is up to the designer or architect to provide for 
when the room is built. 

If no conveniences are provided the manager cannot very 
well blame the projectionist if things are not kept in order, 
but if conveniences are provided and the projectionist does 
not keep things in order, then he is not a fit man to have in 
charge of the projection room. 

RUNNING WATER, TOILET.— It is highly important 
that there be a wash basin with running water, and a toilet 
either in or convenient to the projection room. Both of 
these are very essential, and the latter exceedingly so where 
there is only one projectionist. The basin is necessary be¬ 
cause often something will go wrong with the machinery 
and the projectionist will get his hands covered with oil 
and dirt in making necessary repairs. He will also get 
carbon dust on his hands when trimming the lamp, and il 
there be no means of removing this grime, the next time 
he handles the film it is more than likely that considerable 
damage will be done to it. Moreover, he is apt to soil 
everything he touches. The installation of a wash basin 
and running water is, therefore, highly important. Toilet 
facilities should be required by law, since in many cases 
the projectionist cannot leave the projection room for 
hours at a stretch. 

PROJECTION ROOM CHAIR. —Some theatre manage¬ 
ments will not allow their projectionist to use a chair. This 
is, we are firmly convinced, not only a mistake, but a very 
serious one. One thing imperatively necessary to high class 
projection is that the projectionist remain constantly at his 
post beside the projector. Exhibitors constantly and rightly 
complain that projectionists will not remain at the observa¬ 
tion port, where they belong, and that the projection in 
their theatres suffer by reason of this fact. 

We believe there is several times the likelihood that a 
projectionist who is standing on his feet will move around 
the room than there is if he is seated. The man who is 
seated at his projector in front of the observation port is 
likely to stay seated unless something happens which re¬ 
quires that he get up. The idea that a projectionist seated 
beside his projector cannot do just as good work as he 
would if standing up is pure nonsense. When the author 
was a projectionist he always did his work seated beside 
the projector. Standing several hours on his feet in one 
position or place would have been to him almost an im- 


322 


HANDBOOK OF PROJECTION FOR 


possibility. He was entirely able, while seated at the pro¬ 
jector, to make any necessary adjustment, and to make it 
just as quickly as though he were standing. If anything 
happened it required about l/10th of a second for him to 
rise. There is neither rhyme, reason nor common sense in 
the refusal of a chair to the projectionist. The wise man¬ 
ager instead of refusing the chair would see that one was 
placed at each projector, and demand that the projectionist 
use it, on the theory that when using the chair he would 
“stay put” where he belongs beside the projector while the 
show is running. 

PROJECTION ROOM REELS. —For many years the Pro¬ 
jection Department of the Moving Picture World has recom¬ 
mended that theatre projection rooms be equipped with a 
full complement of projection room reels, and that the reels 
upon which the films are received from the exchange be only 
used in the upper magazine of the projectors the first time 
the films are projected (not even then if the films be first 
rewound or inspected), and on the rewinder when the film is 
rewound for the last time before shipment to the exchange. 

Excellent reason for this recommendation is found in the 
utterly wretched condition of the great majority of reels used 
by exchanges for shipping films to theatres, and in the fur¬ 
ther fact that many exchanges have in the past purchased, 
and at this time (1922) still are purchasing, are too cheap, 
flimsy and rough to be fit for use on a projector, or for 
anything else, for that matter. 

A literally enormous amount of damage to film is caused 
by crooked, rough reels, and reels having a too-small hub 
diameter. Such reels are an outrage upon common sense, 
and the fact that exchanges purchase and use them, or have 
purchased and used them, is by no means complimentary to 
the good business judgment of exchange owners and man¬ 
agers. An exchange may “save” ten cents by winding a new 
roll of film on a bent, rough, cheap reel, and may, in the 
process, lose many times that sum by the actual, though 
not always visible damage done to the film itself. 

At the time of the compilation of this book two really 
excellent projection room reels were presented for examina¬ 
tion and test; also at least one more was in process of 
making. Both those presented were of such construction that 
they deserve commendation, and both are therefore recom¬ 
mended to the favorable consideration of users of this book. 


MANAGERS AND PROJECTIONISTS 


323 


FILMFAST REEL. —The reel known under the trade name 
of “Filmfast Reel” is designed wholly for use in the projec¬ 
tion room. It is a substantial, well constructed reel from 
every viewpoint. The patentee of the reel is Walter I. 
Tuttle, president of the Frank Mossberg Company, the 
address of which firm will be found in their advertisement 
elsewhere. The dimensions of the reel are inches out¬ 
side diameter, with a barrel (hub) diameter of 4% inches. 
In and on the hub, or “barrel” is an excellent film gripping 
arrangement, which facilitates threading by enabling the pro¬ 
jectionist to readily at¬ 
tach the end of the film 
to the reel with one 
hand. 

The sides of the reel 
are of heavy sheet steel, 
of a quality selected en¬ 
tirely with reference to 
the duty it has to per¬ 
form. The sides are 
heavily embossed, 
which together with the 
heavy weight metal will 
prevent kinking, bend¬ 
ing or warping even 
under pretty rough 
usage. The hub con¬ 
struction is very sub¬ 
stantial. It has a cen- Figure 90a. 

tral half-inch-diameter 

stud, drilled and reamed to fit accurately on the take-up 
spindle. This stud is a driving fit into a heavy washer at each 
end, which prevents the key ways from spreading. The two 
washers are joined to each other through the side plates by 
means of three studs which are riveted into the washers. 

The barrel (hub) is attached to each of the reel sides by 
means of twelve metal ears, which same are clinched down 
tight. On the outer surface of the barrel (hub), and con¬ 
centric with it, is a heavy spring attached to its middle por¬ 
tion. To either end of this spring is attached triggers, which 
same extend within the barrel and form a gripping arrange¬ 
ment for the finger, as is shown in Fig. 90a. The projection¬ 
ist pulls on the trigger raising the end of the spring, and with 
the thumb of the same hand slips the film end under the 



324 


HANDBOOK OF PROJECTION FOR 


spring. It is all done with one motion and with one hand, 
and is a positive gripping of the film end. 

The “Filmfast” reel will be shipped you packed in indi¬ 
vidual corrugated paper cartons, which insures their receipt 
in good condition. We recommend the reel to your favorable 
consideration. 

SIMPLEX AUTOMATIC SIGNAL REEL— The Precision 
Machine Company, Inc., manufacturers of the Simplex pro¬ 
jector, is marketing a projection room reel under the above 
name. This reel appeals to us as a very practical, high grade 

proposition for projec¬ 
tion room use. 

In the first place, as 
will be seen in Fig. 90c, 
the sides are of steel 
wire, about 5/64th of an 
inch in diameter. The 
loops are connected to 
the hub, which is five 
inches in diameter, in 
the way shown in Fig. 
90c and Fig. 90d, in 
viewing w r hich you will 
understand that the 
outer shell of the hub 
(F in Fig. 90e), has 
been removed in order 
to show the method of 
connecting the loops to 
the hub studs, the cen¬ 
ter hub itself and the automatic signal device. 

The construction as a whole embodies the following sub¬ 
stantial points of advantage: 

(A) The reel is substantial and rigid. 

(B) It is difficult to bend, and the bending of the reel at 
one point does not affect other portions of the reel; also the 
zone which is bent may be straightened and the reel again 
be made perfect, something which, so far as we know, 
cannot be done with any sheet metal side reel. 

(C) The form of construction and the form of material 
used effectually prevents the cutting or scratching of film, or 
the cutting or scratching of the projectionists’ hands, both of 
which are very common with the cheap sheet metal side reels 
now in general use. 



Figure 90b. 

Filmfast reel with sides removed 
showing hub construction. 


MANAGERS AND PROJECTIONISTS 325 

(D) The open construction of the reel is such that, while 
it affords ample protection to the film, it makes the reel very 
accessible for threading, etc. 

(E) The hub of the reel is the best we have yet seen, in 



Figure 90c. 


that it consists of a solid cylinder of steel, through which a 
hole is drilled to receive the spindle of the take-up or re¬ 
winder. In either end of this steel hub a slot is cut clear 
across the hub, thus forming a double-sided key way. This 
renders it exceedingly improbable, if not impossible that the 


















326 


HANDBOOK OF PROJECTION FOR 


key way will ever wear out, and that is one of the weak 
points in all old style reels; in fact it might be truthfully said 
that the weakest point of the many weak points in old style 
reels was the key way. 

(F) In its center, within the hub, the reel contains an au¬ 
tomatic dissolving signal, as will be explained further along. 

IN THREADING the reel the projectionist passes the end 
of the film under either one of studs A A, Fig. 90c, both 
of which are bright nickeled, being certain the end of the film 
is underneath, as per Fig. 90c. 



Figure 90d. 


IMPORTANT.—The time you will have for making the dis¬ 
solve after the signal is given, depends, within reasonable 
limits, upon the length of the end of the film pulled under 
stud A. The longer this end the more time there will be 
a fter the signal sounds before the screen goes white. 

When you have end E as long as you wish, you must give 
the reel at least one full turn in the direction it normally 
runs, which not only locks the film by friction upon itself 





MANAGERS AND PROJECTIONISTS 


327 


but does another important thing, viz.: Mounted on stud 
B is pivoted arm C, to which the gong hammer is attached, 
as shown. When the reel is given a turn or more to lock 
the film to the hub by friction, it pulls arm C into position 
which holds the gong hammer in the position shown in Fig. 
90d. The action is as follows : Mounted within the shell of 
the hub is a 4-inch diameter gong, marked D in Fig. 90c. 
So long as arc C is held in position, as per Fig. 90d, by the film, 
the hammer cannot stri ;e the gong, but when the last layer 
of film unwinds in process of projection, arm C is released 
and thereafter at every revolution of the reel (and the reel is 
then revolving rapidly) the hammer will strike the gong, 
which is the signal for immediate change-over—in other words 
a signal to immediately dissolve and change to the other pro¬ 
jector. 

We can recommend the Simplex Automatic Signal Reel to 
the favorable consideration of our readers. 

PROJECTION ROOM SUPPLIES.— It is impossible to 
imagine a more foolish and utterly mistaken policy on the 
part of a theatre management than niggardliness in the 
matter of projection room supplies. The suspicion held by 
some theatre managers that if they do not constantly “sit 
on the lid” in the matter of projection room supplies waste 
will occur, is as foolish as it is unworthy. 

The projectionist who cannot be trusted to be careful 
and economical with supplies is not a fit man to be in the 
projection room at all. 

Many theatre managers, however, have a mistaken idea 
of what constitutes economy in supplies. 

The competent projectionist does not wait until a part 
breaks down entirely, thus perhaps stopping the show until 
repairs are made, nor does he wait until a part is so badly 
worn that the screen result is made to suffer. He renews 
parts before a break comes or before there is damage to 
the screen result. 

From any and every viewpoint it is false economy to at¬ 
tempt to get the last possible bit of wear out of projection 
room equipment. Take, for example, asbestos wire lamp 
leads. Entirely too many projectionists use their lamp 
leads, particularly that portion inside the lamp house, alto¬ 
gether too long. Inside the lamp house the wires are sub¬ 
jected to increasing heat from the arc as they approach 
nearer to it, and as the temperature of metal rises its re¬ 
sistance also rises. Copper oxidizes under the action of 


328 


HANDBOOK OF PROJECTION FOR 


heat, and where a wire which is working close to capacity 
electrically is subjected to the action of heat from an out¬ 
side source, .the effect is to raise the resistance of the wire, 
thus lowering its carrying capacity and setting up still more 
heat and rapid oxidization and deterioration. In a very 
short time the strands of the asbestos wire inside the lamp 
house turn brown, then dark brown. 

If you strip back the insulation you will probably find the 
wire to be discolored for a considerable distance. Under 
this condition its resistance is very high, and since resist¬ 
ance means loss which is registered on the meter, the wire 
is consuming within itself, by reason of its high resistance, 
wattage which in a few hours’ time will more than equal 
the cost of the wire, modified, of course, by the fact that if 
current is taken through an adjustable rheostat there may 
be no actual loss, as that much less resistance will be re¬ 
quired in the rheostat. But the condition is a bad one 
nevertheless. 

Yet it is a fact that many theatre managers, lacking 
knowledge of such matters themselves, and unwilling 
to trust the knowledge of their projectionist, protest against 
the cutting off of burned wire, and demand that it be used 
longer. They are “saving” a few cents in wiring deplace¬ 
ment at the expense of a great many cents in electrical 
energy. 

There is always a tendency to use the intermittent 
sprocket of the projection machine too long, with conse¬ 
quent damage to the film and to the screen result, and any¬ 
thing which damages the screen result is expensive, because 
the public patronizes a theatre in proportion to the pleasure 
it gets out of what it sees on the screen. 

I mention these two examples merely as being typical, and 
place them in evidence as showing that it does not pay to be 
too economical in the matter of projection room supplies; 
also as proof that lack of knowledge often causes a theatre 
manager to practice that which is in fact false economy; in 
other words to practice economy which is as a matter of 
fact not economy at all, but exactly the opposite. 

It is the part of wisdom for the theatre manager to em¬ 
ploy only projectionists in whose ability he has at least a 
reasonable amount of confidence, and having done so to 
allow them a reasonably free hand in the matter of pro¬ 
jection room supplies. 

As a matter of business the theatre manager may very 


MANAGERS AND PROJECTIONISTS 


329 


well require his projectionist to keep a record of (a) all 
supplies purchased, (b) make weekly report of repairs and 
replacement, and (c) that all old machinery parts replaced 
be delivered to the manager’s office. 

PROOF. —In proof that it does not pay to be too economi¬ 
cal in supplies, let us cite the following: We believe almost 
any projectionist will agree to keep both projectors in 
first class condition for a year for the sum of $150, this not 
to include ordinary deterioration of the machine as a whole, 
but merely a sufficient replacement of worn parts to keep 
the projectors in first class repair. $150 a year amounts to 
41 1 / 10 cents a day. A theatre of 700 seating capacity giving 
four shows a day has 2,800 seats to sell, or 2,800 admissions 
to dispose of each day. Supposing the admission price to 
be 15c., it would only require the price of less than three 
seats to keep the projection machines in absolutely first 
class mechanical condition, and 

Is there a theatre manager on earth who does not realize 
and know that projectors in first class mechanical condition 
will produce a sufficiently better screen result than pro¬ 
jectors in poor mechanical condition, to increase seat sales 
by an average of three a day out of 2 , 800 ? 

NEW PROJECTORS VERSUS OLD.— The foregoing 
argument applies equally well to the projector as a whole. 
Let us assume John Jones to own a theatre having 700 
seats, giving four shows a day. He therefore has 2,800 
admissions for sale each day. Let us assume his admission 
price to be 20 cents. John Jones has two old type pro¬ 
jectors which should have been thrown into the scrap heap 
long ago. He says he cannot afiford to replace them with 
new projectors. Let us examine into the matter. 

Two new projectors of late type would cost him let us 
say $1,200 for the sake of easy figuring. Let us further 
assume that the new projectors will last three years, at the 
end of which time they will be utterly useless. In other 
words, that John Jones, after using the new projectors three 
years, is going to throw them into the scrap heap as having 
no value at all. Let us 1 also allow 8 per cent, interest on 
the investment. This means that John Jones is going to in¬ 
vest $1,200 in projectors, which at the end of three years 
will be entirely worn out. He will also lose the interest on 
that sum for three years, which at 8 per cent, amounts to 
$288. John Jones therefore stands to “lose” $1,488 in three 
years if he buys two new projectors. This means that in 


330 


HANDBOOK OF PROJECTION FOR 


1,095 days 148,800 cents will have been “used up.” This is 
an average of about 135 cents a day, or the value of less 
than seven admissions at 20 cents each. 

Does that exhibitor live who honestly believes that 
two new projectors will not produce a sufficiently better 
screen result than his worn and more or less out-of-date 
projectors to increase the patronage of the theatre which 
has 2,800 seats (or even a much less number) to sell every 
day by decidedly more than six additonal admissions? 

We thus see that, as a plain matter of common sense, 
John Jones CAN afford to put in new projectors; also that 
he is actually losing money every day he delays doing it. 

The projection room should have an ample supply of 
carbons and all those various repair parts and other things 
necessary to the keeping of the equipment in first class 
condition. It is impossible to enumerate the various things, 
because they will, in the very nature of things, vary con¬ 
siderably in different projection rooms. 

The things we seek to do in the matter of projection room 
supplies is not so much to supply a list, which may or may 
not fit the individual requirement, but to impress upon the 
mind of the theatre management the fact that “scrimping” in 
projection room supplies is, in the long run, not true 
economy, and may actually be a great source of waste. 

AN EXCELLENT FILM CABINET.— The American Film- 
Safe Corporation, Baltimore, Md., is putting out a film 
storage cabinet which we regard as being pretty nearly ideal. 
In fact we very much doubt if the general design of this 
particular piece of projection room equipment will ever be 
very much improved upon, though that prophecy does not 
extend to structural details. The cabinet seems to combine 
about every desirable feature, in that it is fireproof as a 
whole and as applies to individual reel containers, is hand¬ 
some in appearance, rigid in construction, very elastic as to 
capacity. 

In Fig. 90A we have a view of the cabinet, which is named 
the Safe-T-First Film Cabinet, with the notation that in its 
final design each section holds five (5) reels, whereas the one 
shown accommodates three reels to the section. As it now is 
the 5-reel section is the minimum. The 3-reel section is no 
longer made. 

The cabinet is of all steel, insulated construction. In ap¬ 
pearance it exactly resembles the rather handsome cabinet 
document files seen in many offices. Each handle is attached 


MANAGERS AND PROJECTIONISTS 


331 



to and operates the door of a single reel compartment, which 
same is fire insulated from every other single reel compart¬ 
ment. Each of these single reel compartments is, or may be, 
connected either with the open air or with the projection 
room vent flue, through the 
cabinet vent pipe. In other 
words, the vent pipe top, or 
cone, seen at the top of 
the cabinet in Fig. 90e, 
connects directly w,ith 
every one of the single reel 
compartments of the cabi¬ 
net, hence should a reel in 
any one of the compart¬ 
ments catch fire, it would, 
due to the very limited air 
supply, burn very slowly, 
all the smoke being con¬ 
veyed directly away and 
out of doors. This feature 
alone we regard as of dis¬ 
tinct value. 

In Fig. 90f we see one 
of the sections being lifted 
away. Remembering that 
the Safe-T-First cabinet 
sections may not be had in 
less than 5-reel capacity, it 
is seen that any desired 
capacity may be had in a 
single cabinet by piling as 
many sections as desired, 
one upon another; each 
compartment connecting Figure 90e. 

with the vent flues of the 

other sections, as shown in Fig. 90f the flues of the upper 
section being capped by the cone shown in Fig. 90e. 


INDIVIDUAL LOCKS. —Each individual reel compartment 
may be provided with a lock, if so ordered; also each com¬ 
partment is self closing. By opening the compartment the 
reel is automatically moved to the position shown in 
Fig. 90e. 

You cannot leave a compartment open, unless you de- 


332 


HANDBOOK OF PROJECTION FOR 


liberately block it open, because it closes automatically by 
its own weight. 

This cabinet has the hearty indorsement of the author of 
this book and of the Projection Department of the Moving 
Picture World. They are well worth their price. 



THE REWINDER. —The rewinder may be located either 

in the projection room or 
in a room immediately ad¬ 
joining. It will pay the 
projectionist to give a lit¬ 
tle thought to the arrange¬ 
ment of his rewinding 
table. In the first place 
it is of huge importance 
that the two elements of 
the rewinder be in per¬ 
fect line with each other, 
since otherwise the edge 
of the film will rub on the 
edge of the reels during 
the whole process of re¬ 
winding, with resultant 
weakening of the film 
track, especially if the 
sides of the reel be bent 
or crooked. 

We cannot emphasize 
too strongly the import¬ 
ance of carefully lining 
the two elements of the 
rewinder. Damage aggre¬ 
gating thousands of dol¬ 
lars a day is done to film 
by rewinders because of 
the two elements being out 
of line with each other. 
Figure 90f The two elements of the 

rewinder should be placed 
a convenient distance apart, carefully lined with each other 
and fixed firmly and permanently in position so that they 
cannot possibly get out of line. Between the two elements 
of the rewinder a hole about 3 inches wide by 4 inches long 
should be cut in the rewinder table. This hole should be 
covered with a piece of thick glass, the top of which should 


MANAGERS AND PROJECTIONISTS 


333 


be thoroughly ground by rubbing it with fine sandpaper, or 
with fine sand under a piece of flat stone or iron. Under 
this glass install a small incandescent globe, and just back 
of it cut a hole in the table to receive the cement bottle. 
You thus have everything convenient for making splices. 

The rewinder should in all cases be motor driven and 

The speed should be geared down by means of suitable 
pulley wheels or gears until at least 8 minutes is consumed 
in rewinding 1,000 feet of film. 

Rewinding film at high speed is bad practice. If the re¬ 
winding be done at the rate of 8 minutes to the thousand 
feet (10 is better) the film will be rewound in ample time 
to make room for the next reel, in theatres where sane 
projection methods are practiced, and there will be no 
necessity to watch the process of rewinding, unless there 
are repairs to make. There should be an arrangement which 
will automatically stop the rewinder motor when the pro¬ 
cess of rewinding is finished. This may be done in any one 
of a dozen ways, all of which have from time to time been 
described in the projection department of the Moving 
Picture World. Where the motor rewind is used a brake 
should be provided for the reel from which the film is 
being rewound, and there should be just sufficient tension 
to cause the film to be rewound snugly. 

Pulling down of film (holding one reel stationery and re¬ 
volving the other to tighten the film roll thereon) is pro¬ 
ductive of enormous damage to film in the form of scratches 
made as the layers of the film roll slip on each other. 
These scratches later fill up with dirt and form the rain 
marks with which we are all so familiar. If rewinding be 
done by motor, and be done slowly, with plenty of tension 
on the reel from which the film is being rewound, there will 
be no necessity for “pulling down,” and thus much damage 
to film will be avoided. 

Another argument in favor of the slow motor rewind is 
that where rewinding must be done by the projectionist, if 
the speed of rewinding be slow and the rewind be motor 
driven, there is no necessity for the projectionist watching 
the process. He is therefore free to attend to his other 
duties, and if the rewinder be so arranged that the motor 
will automatically stop when the process of rewinding is 
finished, the only attention the projectionist need give the 
process of rewinding is to take off the rewound reel, put it 
in the storage case, put on the reel to be rewound and 


334 


HANDBOOK OF PROJECTION FOR 


start the rewinder going. This, of course, being true only 
when there are no repairs to be made. 

For the purpose of making repairs it is, perhaps, best to 
install a separate hand rewinder. In this connection, we 
would recommend the installation as a part of the pro¬ 
jection room equipment of the film splicer made by the 
General Machine Company, 363 East 155th Street, New 
York City. We have had this little device very thoroughly 
tested. It is low in cost and operates perfectly. See 
Page 277. 

AMMETER AND VOLT METER.— In the judgment of 

the author it is an exceedingly good investment to provide 
the projection room with an ammeter and volt meter, par¬ 
ticularly the former, and to locate them in such position that 
they will be constantly in view of the projectionist when he 
is in working position at the projector. The ammeter 
should be connected to the projection circuits in such way 
that it may be used to indicate the amperage of either arc. 

There is a certain point at which the projection arc will 
produce maximum illumination with a minimum of current 
consumed. Just a slight movement of the carbons away 
from this position will raise the current consumption any¬ 
where from 5 to 20 per cent., without in the slightest degree 
increasing the screen brilliancy—in fact it is likely to de¬ 
crease it. With an ammeter placed directly in view of the 
projectionist he is able to, and if he is a careful man will, 
maintain his arc at the point of maximum brilliancy with a 
minimum current consumption. We are firmly convinced 
that in the average theatre a projection room ammeter, if 
properly located, will pay for itself in a very short time. A 
very good ammeter and volt meter may be had from the 
United Theatre Equipment Corporation, 45 West 45th Street, 
New York City. The method of connecting an ammeter 
and volt meter is shown in Fig. 91. 

ANCHORING THE PROJECTOR.— With modern late 
type projectors anchoring is not of such prime importance, 
since the weight of the machine itself is sufficient to hold 
it steady, and pedestal projectors are designed to be bolted 
to the floor. Anchor bolts may be set in a cement floor by 
drilling holes about 3 inches deep in the cement, setting 
the bolt head down in the hole, and pouring the hole full of 
melted solder. With the lighter machines, however, many 
of which are still in use. the anchoring of the machine to the 
floor is important, since the slightest vibration or move- 


MANAGERS AND PROJECTIONISTS 


335 


ment of the projector will produce unpleasant results upon 
the screen. The old style tables may be anchored down by 
the use of screw eyes set in the floor, wires attached to 
the machine table and to the screw eyes through a “turn 
buckle” such as may be had from any hardware store. We 
do not believe a detailed description is necessary, because 
the^ importance of anchoring a light machine is self-evident, 
and certainly any man fit to be a projectionist would have 
sufficient ingenuity to find a method of securing the de¬ 
sired result. 

TOOLS. —The projectionist should be in possession of a 
kit of tools enabling him not only to do any work incident 



to projection, but small repair jobs as well. Such a kit 
will cost quite a bit of money, but it is a good investment. 
The manager is likely to have a great deal more respect for 
the projectionist who owns a good kit of tools than for one 
who owns a ten cent screw-driver and a pair of pliers. 

In the third edition of the handbook we gave a list of 
tools, to which we see no reason for either adding or sub¬ 
tracting, except to remark that the management should 
provide a small hand bellows, particularly if a motor gene¬ 
rator set to be used. This tool should be a part of the 
projection room equipment. It is used for the purpose of 
blowing out dust and dirt from around the armature and 
pole pieces from the motor generators. The following is 
the list of tools: 

One pair “button” pliers 8 or 10 inch ; one pair 8 or 10 inch 
lineman’s side cutting pliers (we leave the matter of size 
open, as some prefer one and some the other) ; one pair 8 
or 10 inch gas pliers: one large and one medium screw¬ 
driver; one screw-driver with good length of carefully 








336 


HANDBOOK OF PROJECTION FOR 


tempered blade for small machine screws, to be heavily 
magnetized so as to hold small screws; one pair of pliers 
for notching film, see page 288, one small riveting hammer ; 
one carpenter’s claw hammer; one small cold chisel; one 
medium-sized punch; one very small punch for star and cam 
pins ; one small pair tinner’s snips; pair blunt-nose film shears 
(such as clerks use) ; one small gasoline torch for soldering 
wire joints ; one hack-saw. With this kit you will be able 
to do almost any ordinary job, but you will have use for 
them all. In addition to the above the house manager should 
furnish one 8 and one 10 inch flat file, one ^ round file, 
one 8 inch “rat tail” file, a small bench vise with anvil and 
some soldering flux and solder wire, and a film splicer. 

Of course many projectionists will wish to add to this kit, 
but what we have named will serve very well, taken in con¬ 
junction with the files and other things furnished by the 
management. 

SMALL, PRACTICAL BLOW TORCH.— Realizing that in 
order that wire joints be properly made, and that wires be 
properly soldered to terminal lugs at switches, fuse block 
terminals, etc., it is essential that the projectionist have a 
blow torch; also realizing that the average projectionist will 
not go to the expense of purchasing a large blow torch, and 
that if he did it would be an unwieldy thing in the tool kit, 
we have for several years tried to find a small torch, which 
while a substantial and a practical tool, was one which would 
not go “blooy” in a few weeks or months. It was a hard thing 
to find, but we have at last succeeded. 

Messrs. Baum and Bender, Newark and Jersey City, New 
Jersey, make such a tool. Price, post paid, $1. Weight 5 
ounces. Size 5 inches long by about 1 inch in diameter*. 
Material solid brass throughout, except for a wick and 
small rubber tube about a foot long. Flame: very hot and 
about % inch in diameter by 2 to 2inches long. Fuel: 
wood or denatured alcohol. Cost of operation, almost 
nothing. 

OPERATION. —Unscrew lower end cap and fill with 
alcohol. Replace lower cap and remove upper end cap. 
Blow through hose and adjust blow-hole to proper height 
as per instructions accompanying torch. That is all there i$ 
to it. The torch is NOT good for any but very small jobs, 
and for wire joints. It should, except for renewal of the 
rubber hose (cost about 10 cents), and the wick (probably 
5 cents) perhaps once a year, last for years, provided you 


MANAGERS AND PROJECTIONISTS 


337 


don’t allow it to get smashed. We recommend it to you for 
the purposes named. 

TOOLS IN ORDER.— It is of the utmost importance that 
the projectionist’s tools, be they many or few, be kept in 
order, neatly arranged on the wall, the screw-drivers and 
pliers within handy reach. One of the most reprehensible 
habits possible is that of dropping tools when one has 
finished using them and letting them lie until needed again. 

It would be hard to estimate how many thousands of 
times moving picture theatre audiences have sat in the dark, 
waiting patiently while a projectionist searched for the 
pliers, screw-driver, or other tool needed to make a repair, 
which he had thrown down wherever he happened to use it 
last. Often I have gone into projection rooms and found the 
tools lying on the floor in a jumbled pile underneath the 
projector. This kind of thing is not only exceedingly un¬ 
workmanlike, but also is decidedly sloppy. The man who 
does things that way is unlikely to make any large success, 
either of projecting or anything else. 

My advice to the projectionist is have a good kit of tools 
and keep them neatly arranged and in perfect order. 

My advice to the manager is to discharge the projectionist 
who is satisfied to own only a pair of pliers and a screw-driver 5 
or who, having other tools, does not keep them in order. 
If he is unworkmanlike in so important an item, it is likely 
he will be unworkmanlike in other things which will reflect 
directly on the screen in the shape of faulty projection. 

ANNOUNCEMENT SLIDES. —It is frequently necessary 
to make announcements to the audience. There are a greal 
many different ways in which very good appearing slides 
can be quickly prepared. There are inks on the market, in 
several colors, with which one may write, using an ordinary 
pen, on clean, plain glass, just the same as he could write 
on paper. There are also a number of slide coatings for 
sale on which writing may be done with a pointed instru¬ 
ment. These slide coatings are particularly to be desired 
for any slide which must be made on the spur of the 
moment, by reason of the fact that a number of them can 
be gotten ready and laid up on a shelf in a pile, where they 
will keep indefinitely. If anything happens and you wish to 
say something to the audience, the projectionist can write 
on these slides with anything having a sharp point. For 
instance, suppose something occurs that will cause a delay 
of two minutes. Within five seconds the projectionist can 


338 


HANDBOOK OF PROJECTION FOR 


write on one of these slides “Unavoidable Delay of Two 
Minutes,” stick it in the stereopticon and project it to the 
screen. The audience will then be satisfied to wait for that 
length of time. I only suggest this as one possible way in 
which slides of this kind may be utilized. They should be 
kept in the projection room ready for instant use. Please 
understand in this I am not referring to program slides 
which the manager himself will wish to prepare, but merely 
these designed to be used for emergencies. See Page 811. 

WIRING THE PROJECTION ROOM.— The wiring of the 
projection room is a matter which should be carefully 
planned before the construction of the room is begun, es¬ 
pecially if the walls in which the conduit is imbedded are 
to be of concrete or brick. 

The projection room service wires must, of course, be 
large enough to carry the entire load of the projection room 
without overload, and with only about 2 per cent, 
voltage drop. By this we mean that if there are, for in¬ 
stance, two projection lamps, a dissolving stereopticon, a 
spot light and four incandescent lamps; the projection 
room feed wires must be large enough to carry the com¬ 
bined amperage of all these lamps when they are all burn¬ 
ing; though they need only operate at 2 per cent, voltage 
drop at the normal load used. It is quite true they are not 
likely to ever be all in use at one time, but this doesn’t alter 
the fact that the correct procedure is to make the wires 
large enough to supply them all without overload. 

The necessary amperage capacity of the projection room 
feed wires is computed as follows: First estimate the com¬ 
bined amperage. Suppose there are two projectors and you 
propose using 60 amperes at the arc of each through re¬ 
sistance. This would call for 60 + 60 = 120 amperes at the 
two projector arcs. The dissolving stereopticon will, if one 
be used, probably require a total of 30 amperes for the two 
lamps, and if there be a spot light 25 amperes will probably 
serve for it. We will assume the incandescents to require 
five amperes. . We thus have 120 + 30 -f 25 4- 5 = 180 
amperes. Turning to table 1, Page 70, we find that if the 
service circuit be 2-wire it will be necessary to install 
No. 000 wires to carry that amount of current without over¬ 
load, modified by the fact that length of circuit forms an 
element which must be reckoned with. See “Figured Volt¬ 
age Drop,” Page 74. 

If the feeders are 3-wire, then, since when the lamps are 


MANAGERS AND PROJECTIONISTS 


339 


all in use one-half would burn in series with the other half; 
providing the balance be perfect (see 3-wire system, Page 
85), the amperage requirement would thus be cut in half 
and No. 2 wires would serve, again provided length of 
circuit be not too great. 

If the projection room service circuit be 3-wire, but it be 
required that the projection arcs be connected across the two 
outside wires on 220 volts, then it would be necessary that 
the two outside wires have the same capacity as though it 
were a 220 volt 2-wire system. 

However, regardless of what the condition may be, the 
projectionist should figure the voltage drop as per the 
formulas laid down on Page 74, since voltage drop due 
to too high resistance of the projection room service wires 
will be registered on the meter, and must be paid for just 
the same as though the current were consumed at the arcs, 
modified when current is taken through adjustable resist¬ 
ance. In that case the excess resistance in the wires may be 
compensated for by using less resistance in the rheostat, 
but the condition, nevertheless, is a bad one. 

If all the lamps be operated from motor geenrator set, 
rotary converter or motor arc rectifier, or through a low 
voltage transformer (economizer, compensarc, inductor, etc.) 
then the projection room service wires need only be 
large enough to supply the primary capacity of these de¬ 
vices, always assuming the aforesaid motor generators, 
rectifiers or transformers are to be supplied by the pro¬ 
jection room service circuit. If they be located in the base¬ 
ment or elsewhere and the projection room be supplied by 
wires from them, then, of course, since these wires will 
carry the secondary current, their size must be figured on 
that basis. 

In Fig. 92 the general layout of a projection room switch¬ 
board is shown. There should be a main switch (A) sup¬ 
plied with link fuses (B-B-B). This switch and the fuses 
carry the entire projection room load. The incandescent 
circuits should be taken through a separate circuit con¬ 
trolled by a separate knife-switch as per C. Cut out blocks 
D-E-F (there may be as many as are required), carry fuses 
for the various circuits and, if desired, switches also. In 
Fig. 92 we will assume circuits 1 and 2 supply the projector 
arcs, circuits 3 and 4 the dissolving stereo circuit and cir¬ 
cuit 5 the spotlight. This layout is only designed to be sug¬ 
gestive. It shows how a very acceptable projection room 


340 


HANDBOOK OF PROJECTION FOR 



Figure 92. 




































































MANAGERS AND PROJECTIONISTS 


341 


switchboard may be built up from switches and fuses 
mounted on a suitable insulating base. The board shown in 
Fig. 92 is built of inch asbestos mill board and is en¬ 
closed in a metal cabinet similar to the one shown in Fig. 
17, Page 104, only larger. This type projection room 
switchboard may easily be constructed by using slate-base 
knife-switches equipped with fuses, if it is so desired; and 
it is quite practical to use link fuses instead of cartridge 
fuses-. In fact in some cities this is required by law for 
projection circuits. 

BALANCING THE LOAD. —Where a 3-wire service cir¬ 
cuit supplies the projection room, and it is permitted that 
connection be made to the neutral, the power company 
should in all cases be consulted as to how they would prefer 
to have the projection arcs connected. It is, of course, im¬ 
possible to balance the projection room load on a 3-wire 
system, because ordinarily only one projection arc will be 
burning at a time. This, however, does not apply to the 
dissolver, the arcs of which should always be connected to 
opposite sides of the system, since when the dissolver is 
used its load will be perfectly balanced between the two 
sides. If both dissolver lamps were connected on one side, 
when the dissolver is in use, it would have an unbalancing 
effect of whatever the capacity of the two dissolver lamps 
may be. Ordinarily it would be undesirable to connect both 
projection lamps to one side, particularly if you are using 
high amperage, because when the arc of the idle projector 
is struck to heat the carbons before it is time for a change 
over, for a short time the entire load of both projectors 
would be on one side of the system, which would mean an 
unbalancing effect of anywhere from 60 to 200 amperes (or in 
some cases even more) which would be sufficient to be ob¬ 
jectionable even on a system, supplied by large generators. 

As a rule power companies will always want projection 
lamps connected on opposite sides, but as we said in the be¬ 
ginning it is good practice to consult them in a matter of 
this kind. In the foregoing we are assuming the arc lamps 
to be taking current directly from the mains through re¬ 
sistance. 

CONNECTING MOTOR GENERATORS, ECONO¬ 
MIZERS, ETCETERA. —Where current is taken through a 
motor generator set, and the supply lines are 3-wire, we 
would recommend the purchase of apparatus having a 
motor of the voltage of the two outside wires. This not only 


342 HANDBOOK OF PROJECTION FOR 

avoids any unbalancing effect, but has the additional ad¬ 
vantage that high voltage motors work more efficiently than 
the low voltage machines. 

Where current is taken through a mercury-arc rectifier, 
and the projection room is supplied by a 3-wire system, we 
would recommend that the rectifier be connected across the 
two outside wires, which may be done merely by making the 
proper internal connections in the rectifier itself. See 
Page 522. 

Where projection current is taken through low voltage 
transformers (economizers, inductors, compensarc, etc.) and 
the projection room feeders are 3-wire, it is better to pur¬ 
chase an economizer to operate on a voltage of the two 
outside wires. Such an economizer is just as efficient as 
the one of lower voltage, and the unbalancing effect is thus 
avoided. 

The location of the projection room switchboard cabinet 
will necessarily be determined by local conditions, but it 
should be remembered that inconveniently located appa¬ 
ratus invariably tends to decrease efficiency of operation. 

There is nothing to be gained by making things incon¬ 
venient for the projectionist. On the other hand there is 
much to be lost by so doing. 

PROJECTION ROOM FUSES. —We would suggest that 
the projection room service fuses be placed as shown in 
Fig. 92, rather than on the other side of the main switch. 
Inasmuch as the projection room feeder circuit, including 
the main switch, is protected by fuses in the main house 
switchboard or elsewhere, there is no necessity for pro¬ 
tecting the main projection room switch further; and it is 
more convenient to install fuses at B if the fuse block be 
“dead” than if it be alive, as it would be if the fuses were 
on the other side of the switch. 

HIGH VOLTAGE THROUGH RESISTANCE.— Some 
power companies will not permit the neutral wire of the 
3-wire system being run to the projection room. This com¬ 
pels the use of 220 volts, which, if rheostats be used, is very 
wasteful indeed. The reason for the refusal to allow the 
neutral to be run to the projection room is the heavy un¬ 
balancing effect of the projection arcs, as already ex¬ 
plained. It is quite possible that this unbalancing effect 
may be very serious, from the power company’s viewpoint, 
especially in a small city where there are a number of mov¬ 
ing picture theatres and the power company’s generators 


MANAGERS AND PROJECTIONISTS 


343 


likely to be pretty heavily loaded. Suppose, for instance, 
a 3-wire street main supplies five moving picture theatres, 
each of which have two projectors, all connected to the same 
“side” of the system. It might very easily happen that the 
projectionists of all five theatres would chance to be chang¬ 
ing from one machine to the other at the same time, and 
that all struck the arcs of their idle projector at approxi¬ 
mately the same time. This would mean, assuming they 
were pulling 60 amperes at each arc, a total unbalancing 
effect of 600 amperes, since while the arcs of both pro¬ 
jectors were burning each theatre would be using 120 



to that side of that particular street main, at least tempo¬ 
rarily. Even if these five theatres each had their two pro¬ 
jection arcs on opposite sides, when only one arc was 
burning in all of them it would mean an unbalancing effect 
effect of 60 x 5 = 300 amperes, so that you see the light 
company is, from their viewpoint, perfectly justified in 
demanding that only the outside wires of their 3-wire system 
be used. 

This does not, however, hold good if current be taken 
through rheostats. 

In that event the compelling of theatres to connect to the 
























344 


HANDBOOK OF PROJECTION FOR 


two outside wires would simply mean that instead of over¬ 
loading one generator by a given amount, both generators 
attached to the system would be overloaded that amount. 
Instead of one generator pulling an unbalanced load of 600 
amperes, as before set forth, if connected to the two outside 
wires each generator would have to pull a load equal to 
600 amperes at 110 volts when all arcs are burning, there¬ 
fore the only result would be a big additonial (double) load 
on the power plant, and an entirely useless waste of elec¬ 
trical energy. 

The reason for this is that when taking current through 
rheostats 600 amperes at 110 volts equals 66,000 watts, but 
600 amperes at 220 volts equals 132,000 watts, the extra 
energy being consumed in the resistance itself. 

While the light company has the undoubted right to de¬ 
mand that the projection lamps be connected to opposite 
sides of a 3-wire system when current is taken through 
economizers, it has no right to demand that the projection 
lamps be connected to the outside wires of a 3-wire system 
if current is taken through rheostats, since it gains abso¬ 
lutely nothing by that sort of procedure except the sale of 
double the amount of electrical energy. 

Where projection current is taken from a 3-wire system 
through either a motor generator rotary converter, mer¬ 
cury arc rectifier or economizer, the power company is en¬ 
tirely within its rights in demanding that the theatre use 
the two outside wires only for projection current. 

PROJECTION ROOM INCANDESCENTS.— The projec¬ 
tion room lighting presents a very distinct optical problem, 
though that fact seems to be seldom realized by either the 
projectionist or the theatre management, and apparently is 
seldom realized or recognized by the architect. It is an 
optical impossibility to have a clear sharp view of a screen 
located perhaps 100 or more feet away when looking out of 
a well lighted room through a comparatively small opening 
in its wall. This is true under any circumstance, but is 
especially true if the walls surrounding the opening (ob¬ 
servation port) be light in color, and since it is impossible 
that the projectionist judge of the fineness of focus unless 
he has a clear sharp view of the screen, it follows that 
sharpness of focus or definition will inevitably suffer if the 
observation port be small, and the projection room unintel- 
ligently lighted. 

After visiting hundreds upon hundreds of theatres in all 


MANAGERS AND PROJECTIONISTS 


345 


parts of the country the writer has never yet seen but one 
in which a really good view of the screen was had from a 
well lighted projection room. This single exception is 
described on Page 311, but since much time will be required 
to educate theatre managements and public officials to the 
large projection room observation port, we must in the in¬ 
terim deal with conditions as they are. The average pro¬ 
jection room has a relatively small observation port, and 
some of them have a very small one. It is difficult to get a 
sharp view of the screen through such a port under any 
condition, and it may be stated as a matter of fact that un¬ 
less projection rooms having these ports are kept dark the 
screen result will inevitably suffer. 

In such rooms we would recommend that where the ceiling 
is high—say not less than 10 feet—a row of lights, say four 
in number, be placed at the ceiling, and as close as possible 
to the front wall, and then that a board or shelf be run 
along the entire length of the front wall extending out just 
far enough to prevent the light from these lamps striking 
the rear wall within 6 feet of the floor, the space above the 
shelf to be painted white. 

This suggestion if properly carried out will set up as 
good an optical condition as could be expected, but it will 
not work if the ceiling is low, because in that event the 
light would shine directly into the projectionist’s eyes. 

With a low ceiling the lights may be placed at will, and 
switches provided so that the projectionist may turn the 
lights out when projecting. 

Another excellent plan for projection room illumination 
is that used by the Cinematograph Theatres, Ltd., England. 
It consists of inverted bowl indirect lighting fixtures in 
which two distinct circuits are installed, one carrying suffi¬ 
cient lamps to illuminate the room very dimly, just enough 
to enable the projectionist to find his way about, the other 
circuit serving to give brilliant illumination. It is forbidden 
that the “bright” circuit be used except in emergency. 

We would suggest that unless some such plan be adopted 
the management of theatres absolutely forbid the burning 
of any incandescents in the projection room when the pic¬ 
ture is running, except in case of emergency or while 
threading the idle machine. The management has a per¬ 
fect right to make this rule, because upon its observance 
depends, to a considerable extent, the continuous excellence 
of screen results. 


346 


HANDBOOK OF PROJECTION FOR 


GROUND WIRE. —It is highly desirable that a perma¬ 
nent, known ground be established in the projection room, 
and this may be best done by attaching a No. 22 or large/ 
copper wire to a water pipe, or else soldering the end of 
such a wire to a copper plate not less than one foot square, 
and burying the plate, imbedded in powdered coke, in the 
ground deep enough to secure a permanent contact with 
moist earth. If the wire is attached to a water pipe the 
pipe should be scraped with a file until it is bright, the 
wire thoroughly cleaned and wrapped around the pipe tight¬ 
ly several times. It will not be practical to solder anything 
to a water pipe if the pipe contains cold water. Another 
and even better plan is to file the pipe clean and then make 
a band, either of brass or copper, and clamp the same to 
the pipe by means of small stove bolts, first having soldered 
the end of the ground wire to the band. Having attached 
the ground wire, either to the water pipe or to the buried 
copper plate, it should be carried to a convenient point in 
the projection room, and the end of it attached to one bind¬ 
ing post of an ordinary incandescent lamp socket, as shown 
in Fig. 93. We then attach another copper wire to the other 
binding post of the lamp socket, this latter wire being long 
enough to reach any part of the apparatus it may be desired 
to test. A good place for the lamp socket is in the ceiling 
immediately above the projectors, unless the ceiling be too 
high, in which case it may be attached to the front wall 
between the two projectors. Having established an ordi¬ 
nary incandescent lamp in the socket, testing for grounds 
becomes a very simple matter indeed, since we have only to 
touch the thing it is desired to test with the raw end of the 
test wire (see “Testing for Grounds,” Page 356.) 

We are indebted to John Auerbach, New York City, for a 
most excellent testing installation by means of which it is 
only necessary to close a switch in order to test for grounds 
in either carbon arm, or to test the fuses even though they 
be located at a distant point as, for instance, in the base¬ 
ment. 

The following is the key to the diagram shown in Fig. 93: 

(A) Incandescent lamp. 

(B) Incandescent lamp. 

(C) Single Pole Snap Switch. 

(D) Single Pole Snap Switch. 

(E) Single Pole Snap Switch. 

(F) Single Pole Snap Switch. 


MANAGERS AND PROJECTIONISTS 347 

(G) Wire leading to binding post of positive carbon arm. 

(H) Wire leading to binding post of negative carbon arm. 

(I) Edison 3-wire system. 

(J) Incandescent cutout in projection room. 

(K) Projection circuit cutout in projection room. 

(L) Positive fuse of projection circuit. 

(M) Negative fuse of projection circuit. 

That part of the diagram drawn in heavy lines indicates 
wiring to test for grounds in either carbon arm. That part 
drawn in light lines indicates the wiring to test fuses in 
main service fuses. The device therefore may be wired 



Figure 94. 


for either or both of these purposes. When the tester is not 
in use all switches should be open. 

(A) To test for ground in positive carbon arm close 

switch C. If lamp lights, a ground is indicated in that arm. 

If lamp does not light there is no ground. 

(B) To test for ground in negative carbon arm close 

switch D. If lamp lights, a ground is indicated in negative 

carbon arm; otherwise not. 

(C) To test positive projection room service fuse close 
switch E. If lamp lights fuse is O. K.; otherwise it is not. 

(D) To test negative projection room service fuse close 
switch F. If lamp lights fuse is 0. K.; otherwise it is not. 

Wiring connections to projection cutout should be made 
ahead of the switch and the switch should always be open 















































348 


HANDBOOK OF PROJECTION FOR 


when tests are being made. The projectors should be per¬ 
manently grounded by a ground wire and this ground wire 
should be left connected during the making of the tests. 

TROUBLE LAMP.— A “trouble lamp” should of course 
be installed, and the best way to do this is to place in some 
convenient location a permanent socket containing a plug 
to which sufficient cord is attached to reach any part of the 
room. At the extremity of this cord should be a lamp 
socket and an incandescent lamp of suitable power, covered 
by a wire guard to prevent breakage. 

PROJECTOR CIRCUITS. —As has already been said, 
Page 302, the projector circuits should be carried under the 
floor to a point immediately under each projector lamp 
house, but where circumstances for any reason prevent this, 
or make it difficult, then the projector circuit may be car¬ 
ried above the ceiling, or if that is impractical, then the 
projector circuit may be carried along the ceiling to a point 
just to the rear of the lamp house, whence the conduit may 
drop down to a point just above the rear end of the lamp 
house. There is in fact very little real objection to this 
latter plan, provided the lamp house be piped to the vent 
flue as per Page 363, so that the wires will not be subjected to 
the heat arising from it. 

SWITCH ENCLOSURE.— It is usually required that all 
switches (except those of the enclosed type) and fuses be 
enclosed in a metal cabinet. This requirement unquestion¬ 
ably adds an element of safety, since there is always the 
chance of something falling against an unprotected switch 
or open fuse contacts, and causing trouble; also there is 
always the possibility of the projectionist himself acciden¬ 
tally coming into contact with unprotected switches or fuse 
contacts and receiving a disagreeable shock, or even a burn. 

The projector switch itself must be of the “enclosed” 
type, i. e. enclosed in a sheet metal casing. 

DOUBLE THROW CONNECTION.— It is very bad prac¬ 
tice to connect the two projectors through a double-throw 
switch to the center contacts of which the supply is at¬ 
tached, so that it is necessary to extinguish one projector 
lamp before the other can be lighted. This sort of connec¬ 
tion is only permissible in cases where current is taken 
through a single motor generator or rectifier of such small 
capacity that it cannot supply both lamps, even for a lim¬ 
ited time. Even under this condition it is very much better 


MANAGERS AND PROJECTIONISTS 


349 


to wire in parallel (multiple) and “steal” the current from 
one lamp to the other, than to adopt the above described 
plan. 

Where the motor generator or mercury arc rectifier is too 
small to allow burning both arcs together for even a limited 
time, or where only one economizer is used, Fig. 95 offers 
an excellent plan by means of which the idle lamp may be 
warmed and a crater burned in by means of a rheostat. By 
tracing the connectipns in Fig. 95 it will be found that with 
the switch in the position shown in the diagram the right 



Figure 95. 


hand lamp is taking current through the compensarc while 
the left hand lamp is taking current directly from the sup¬ 
ply lines through the rheostat. When the four-pole switch 
is thrown over the same condition will prevail, except that 
the left hand lamp will then be taking current through the 
compensarc and the right hand lamp through the rheostat. 
The arrangement is a most excellent one under the condi¬ 
tions we have named, and the wiring of the diagram is 
sufficiently plain that any projectionist or electrician should 
be able to make the installation without trouble, substi- 


















































350 


HANDBOOK OF PROJECTION FOR 


tuting either a motor generator or a mercury arc rectifier 
for the compensarc, if either one of them be used. 

POLARITY CHANGER.— Where the supply is taken 
from a small D. C. plant it sometimes occurs that when 
dynamos are changed the polarity changes, which requires 
the instant switching of your own wires to bring the posi¬ 
tive back to the upper carbon. This may quickly be ac¬ 
complished by the installation of a double-throw double¬ 
pole switch, such as is seen in Fig. 96. Throwing this switch 



over changes the polarity of the wires. The cross wires 
should be protected by flexible insulating tubing in addition 
to their own insulation. 

Fig. 97 is the diagrammatic representation of a combined 
polarity switch and fuse changer. By throwing switch A a 
new set of fuses is brought into use and by throwing switch 
B the polarity at the arc is changed. 

CONNECTING TO TWO SOURCES OF SUPPLY.— For 

various reasons it is frequently desirable to make connec¬ 
tion to two separate sources of electrical supply. One may 
have one’s own light plant, but wish, in case of accident, to 
be able to instantly connect to the wires of the city plant. 
This may be done, but details may vary widely in different 
cases. Suppose, for instance, we have a house plant deliver¬ 
ing direct current at 110 volts, while the city plant produces 
A. C. at 110 volts; both systems two-wire. The problem 
then is simple. 

Install a double-pole, double-throw switch, as per Fig. 98. 
The house plant being D-C, we shall not need nearly so 
much amperage from it as would be necessary for equal 
screen illumination with the city plant, A-C; therefore, we 
install two rheostats, A and C, the lower one, A, to be used 










MANAGERS AND PROJECTIONISTS 


351 


with the D-C house plant. B is a double-pole single-throw 
knife switch which is open when D-C is in use, so as to use 
only rheostat A. When we change to A-C, however, we 
close switch B, thus cutting rheostat C in multiple with 
rheostat A. Rheostat C should have capacity sufficient to 
build the combined amperage of the two up to that neces¬ 
sary for good illumination of the screen. Suppose we use 
35 amperes D-C. In order to secure anything like the same 
curtain brilliancy rheostat C must have capacity sufficient 
to deliver 25 amperes which, combined with the capacity of 
rheostat A, will give 60 amperes at the arc. But we must 
remember that, owing to the shorter A-C arc, hence the less 
arc resistance, rheostat A will deliver somewhat more cur¬ 
rent on A-C than it will on D-C, the voltage of the supply 
being the same in both cases. We will probably, therefore, 
be not far out of the way if we have rheostat C of capacity 
to deliver 20 amperes at the arc. 



We may, however, instead of this, install a transformer 
(economizer, inductor, compensarc, etc.), in place of rheo¬ 
stat C, Fig. 98, and with a triple-pole double-throw switch, 
wired as per Fig. 99, cut out resistance A, Fig. 98, substitut¬ 
ing the economizer therefor. Merely throwing the switch 
over would then change from rheostat to transformer, and 
vice versa, though the transformer would be “alive” in the 
sense that you could get a shock from it. But this would 
do no harm. If you wish to “kill” the transformer entirely 
when using the rheostat, it may be done by installing a 
S. P. S. T. switch at X, Fig. 99. 





































352 


HANDBOOK OF PROJECTION FOR 


Please understand there are many other switch arrange¬ 
ments possible. Such things may be done in many ways. 
Those suggested merely illustrate two possible methods. 
Another and still better way to cut the two rheostats in 
multiple, Fig. 100, is by means of a triple-pole, double-throw 
switch. 

A careful tracing out of the connections in Fig. 100 will 



show that when the switch is thrown to the A-C supply 
side the two rheostats are in multiple, while when the D-C 
side is in use only rheostat 1 is working. Should the supply 
voltage be higher on one system than on the other, a higher 
voltage rheostat could be substituted for A, Fig. 98, and 
rheostat C be made of such capacity that it will bring the 
amperage up to normal when on the lower voltage. 

GROUNDS. —Grounds are perhaps the one most puzzling 
thing to the novice. They also very often tax the knowl¬ 
edge of experienced projectionists. This we believe arises 
partly from the fact that the term, as used, has, strictly 
speaking, more than one meaning. In one sense, a “ground” 
means a current carrying connection with the earth which 
offers a path through the earth to a wire of opposite polar¬ 
ity. When we speak of a ground in a rheostat, we how¬ 
ever do not necessarily mean that there is any connection 
with the earth itself. Two coils may be “grounded” to the 
frame of a rheostat in such way that a part of the resistance 
of the rheostat is eliminated, notwithstanding the fact that 
the rheostat as a whole sets on an insulating shelf, and has 

































MANAGERS AND PROJECTIONISTS 


353 


no possible connection of any kind whatsoever with the 
earth. In its simplest sense the term “grounded” means that 
one wire of a circuit has current carrying connection with 
the earth, though this does not necessarily mean that there 
will be current leakage into the earth. This latter will only 
occur when the ground offers an electric path to a wire of 
opposite polarity which is attached to the same generator. 

EDISON SYSTEM GROUNDED.— The neutral wire of 
all Edison 3-wire systems is permanently grounded to 
earth. This is a true ground, and if an accidental ground 
occurs on either of the other wires of the system there may 
be and probably will be current leakage. 

Right here let us make it clear that the rather common 
belief that current seeks to escape from the wires into the 
ground is entirely wrong, except when by so doing it can 
find a path to a wire opposite polarity which is attached to 
the same generator. See Page 6. Let us also further 
emphasize the fact that: 

Current generated by one dynamo has absolutely no affin¬ 
ity for the opposite polarity of another dynamo except when 


I ] 
I 

! I 



the two generators be electrically connected, as in the 3- 
wire system, in which case they are to all intents and pur¬ 
poses one machine. 

Fig. 101 is a diagrammatic representation of a true 
ground. A is a circuit attached to generator G. B and D 
are subsidiary circuits branching from it, and C is a circuit 
attached to another generator Y. Now let us assume a 
ground to exist at point Z in the lower or negative carbon 
































354 


HANDBOOK OF PROJECTION FOR 


arm of arc lamp F on circuit D, and that a ground develops 
at X on the positive of subsidiary circuit B. Let us also 
assume that a ground exists at X on the negative of circuit 
C attached to generator Y. The result of all this would be 
that although the ground at X on circuit C is considerably 
nearer the ground at X on circuit B than is the ground at 
Z, and that quite possibly it would therefore offer decidedly 



less resistance to the passage of current, the current never¬ 
theless pays no attention to the ground at X on circuit G 
but travels through the earth to point Z where it can enter 
a negative wire attached to its own generator. On the other 
hand should a ground develop in rheostat E, which is on the 
positive of circuit D, and a ground develop at O in circuit A 
the current would enter the earth, follow the dotted lino 
and enter the negative wire at O. 

Let it be understood, however, that it does not necessarily 
follow that because two wires of opposite polarity have 
current carrying connection with the earth there will be 
current leakage, because the ground thus established may 
have such high resistance that ordinary voltage will not 
overcome it. In reaching the earth through a ground the 
current will often follow a devious path through water or 
gas pipes or electric conduits, the latter being always 
grounded. 

The grounding of the 3-wire system is a puzzle to many. 
There are two kinds of 3-wire systems, viz.: The Edison 
system, in which the neutral is always thoroughly grounded, 
both at the generator and at other points along the line; 
and the 3-wire system in which the whole system is insulat¬ 
ed from the earth. The latter system is only used by small 
isolated plants. 

The reason for grounding the neutral in the Edison sys¬ 
tem is to prevent any possibility of the conduit in buildings 
























MANAGERS AND PROJECTIONISTS 


355 


becoming charged at 220 volts, or, to put it in electrical 
terms, to limit the difference in potential between any wire 
in the conduit system in buildings to 110 volts. 

With the Edison 3-wire system, the test lamp will not 
show a light from neutral to ground because the wire is 
already grounded, hence if the carbon arm of your projector 
lamp which is attached to a neutral wire of an Edison sys¬ 
tem be grounded there will be no effect unless your rheostat 
be on the neutral wire, in which case the fuses may blow 
when the arc is struck. This latter is by reason of the fact 
that the striking of the arc completes the circuit through 
the ground, as indicated in Fig. 101, which might eliminate 
the rheostatic resistance, leaving only the resistance of the 
arc and such resistance as the ground may offer, which may 
be more or less than was offered by the rheostat itself. It 
might incidentally be said that theoretically it would be 
quite possible when using an Edison 3-wire system and 
rheostatic resistance to locate the resistance on the outside 
wire, remove the insulation from the carbon arm to which 
the neutral is attached, disconnect it from the wire and 



thoroughly ground the carbon arm, whereupon the arc 
would operate the same as though it was connected to the 
neutral. The above, however, is not a practical thing to do 
because of the fact that any ground which might be estab¬ 
lished would in all human probability offer very much 
higher resistance than would be offered by the copper wire, 
also the resistance offered would probably not be constant, 
but variable and unstable. 






















356 


HANDBOOK OF PROJECTION FOR 


TESTING FOR GROUNDS.— Grounds may be tested for in 
a number of ways. A battery and buzzer or a magneto bell 
may be used. It is even possible to test for ground with just 
a plain copper wire, depending upon the spark resultant 
upon making and breaking contact to disclose the passage 
of current; but the latter plan is not recommended, since if 
the ground be a heavy one a heavy flash and blowing of 
fuses might occur. 

The practical testing tool for the projectionist is, however, 
the test lamp, a permanent form of which is illustrated in 
Fig. 102. For two wire circuits a test lamp consists of a 
socket containing an incandescent lamp of the voltage of 
the system, with two wires attached thereto. These wires 



Figure 102. 


may be of any convenient size and length. Fig. 102 illus¬ 
trates a test lamp to be used either with a 2-wire or a 3- 
wire system, wires A-B being used for testing across the 
two outside wires, and wires A-C for testing from neutral 
to either outside wire. 

Taking Fig. 101 for example, and considering lamp F on 
circuit D as a projector arc lamp, if we disconnect the pro¬ 
jector ground wire, thus insulating the projector from the 
ground, and then touch one wire of the test lamp to the 
upper carbon and the other to the frame of the lamp back 
of the insulation of the lower carbon arm, and the test lamp 
lights; or there is a spark when the wire is rubbed along 
the metal of the lamp frame, we know there is a ground in 
the lower carbon arm. The arc must be not burning and 
the carbons of the lamp must of course be separated when 
the test is made. 

In using the permanent test lamp described in Fig. 93 we 








MANAGERS AND PROJECTIONISTS 


357 


would disconnect the projector ground wire and touch the 
wire of the permanent test lamp to the lamp frame. If 
there is a spark as the wire is rubbed along the metal, or 
if the test lamp lights (sometimes a ground may be existent 
but of such high resistance that there will not be sufficient 
current passing to heat the filament of the test lamp red. 
In this event the ground is detected by the spark at the end 
of the wire) we know one or the other of the carbon arms 
are grounded. If it is an Edison 3-wire system we know it 
is the arm not connected to the neutral. If it is not an 
Edison 3-wire system then we have only to disconnect one 
of the wires of the lamp to determine which arm it is. If 
there is no further evidence of a ground we know the 
trouble is in the arm from which the wire has been discon¬ 
nected. If the test lamp still lights, or there is still a spark 
we know the trouble is in the carbon arm which is still 
“alive.” 

Always disconnect the ground wire of the projector be¬ 
fore attempting to test your lamp for grounds, except when 
using the Auerbach method. 

TESTING WITH BATTERY.— Another simple method of 
testing the arc lamp for grounds is to use a dry battery. 
No bell is necessary. Just connect two wires to the battery 
and, with the projector table switch open, touch one wire to 
the lamp frame and the other to first one and then the other 
carbon arm. If there is a ground there will be a spark, but 
this test should be made in a darkened room, because the 
spark may be faint, due to the low voltage of the battery. 
As a matter of fact the battery test is not very reliable be¬ 
cause a high resistance ground which might let current 
through when subjected to 110 volt pressure might not show 
at all with the battery test. 

The magneto test is of course the best of all, but the pro¬ 
jectionist can hardly afford to add a high-priced magneto 
to his tool kit. The magneto test iS best by reason of the 
fact that the magneto produces voltage very much higher 
than that of any projection circuit. To test the arc lamp 
with a magneto you have only to open the projector table 
switch and connect one of the magneto wires to the lamp 
frame and touch the other alternately to the two carbon 
arms. If there is a ground in the insulation the bell will 
ring. 

With the insulated 3-wire system the test lamp acts ex¬ 
actly the same as it does with the plain 2-wire system. 


358 


HANDBOOK OF PROJECTION FOR 


LOCATING GROUNDED RHEOSTAT COILS.— The 

locating of a grounded rheostat coil or grid is a very puz¬ 
zling thing to the novice, as well as to many projectionists. 
It really is, however, a very simple matter. 

In Fig. 103 we have the diagrammatic representation of a 
rheostat, in which A M C D, etc., are the coils or grids, one 
of which, E, is “grounded to the frame” at X, meaning by 
this that it has current carrying connection with the frame 
at that point. Assuming that we wish to test the rheostat, 



Fig. 103, to find out whether or not it is in good order; using 
a magneto, or a bell and battery, first touch the rheostat 
binding posts with the two leads from the bell and battery, 
or the magneto. If the bell rings it indicates that the circuit 
is complete; that is to say, no coil is broken or disconnected. 
Next touch one binding post (either one) and the outer 
casing of the frame of the rheostat. If you get no ring, 
then the rheostat may be considered as in good order, ex¬ 
cept that, as before indicated, there may be trouble which 
would develop when the rheostat is subjected to full voltage 
which would not be indicated by the low voltage of a bat¬ 
tery, but which would be discovered by a magneto, and 






















MANAGERS AND PROJECTIONISTS 


359 


except for one thing which cannot be located with a bell, a 
magneto or test lamp, viz.: two coils being sagged together, 
which would eliminate a part of the resistance of the 
rheostat without breaking the circuit. 

This latter could only be determined by a physical exam¬ 
ination of the rheostat, or by observation when it was in 
actual use, in which latter event the point of contact be¬ 
tween the two coils or grids might, and probably would 
be, heated sufficiently to become visible. 

Rheostats may be tested with a test lamp in a number of 
ways. First, assuming the rheostat as a whole to rest upon 
insulating material, with the current on, attach your test 
lamp to the frame of the rheostat and to a wire of opposite 
polarity. If there is a spark at the point of contact, or if 
the test lamp lights, the coils or grids are grounded to the 
frame at some point, and the exact point may be located as 
hereinafter described. 

Another method would be to disconnect the wire leading 
from the rheostat binding post, connecting the same to one 
of the test lamp leads then, first having “frozen” the carbons 
of the arc lamp, touch the rheostat frame with the other 
test lamp lead. If the test lamp lights, or if there is a 
spark at the point of contact, then the coils or grids of the 
rheostat are grounded to the frame at some point. If, how¬ 
ever, there is no spark, or if the test lamp does not light, 
then the coils and grids are insulated from the frame. 

Still another way, again assuming the rheostat as a whole 
to rest on insulating material, is to disconnect one of the 
wires from the rheostat binding post and, with the carbons 
of the arc lamp “frozen” and the projector table switch 
closed, touch the disconnected wire end to the frame of the 
rheostat. If you get a spark there is a ground. This latter 
method of course amounts in effect the same as the one 
previously described, except where the test lamp is inter¬ 
posed between the wire and the frame its resistance limits 
the current flow and there is no danger of blowing fuses, 
which might occur if the last test named were applied. 

Suppose we have applied one of the before described tests 
and find there is a ground in the rheostat, indicating that 
one or more of the coils or grids has current carrying con¬ 
nection with the rheostat frame. How are we to discover 
the particular coil or grid at fault? That is the point which 
puzzles so many, but it is a point which becomes very 
simple when we examine it in the light of common sense. 


360 


HANDBOOK OF PROJECTION FOR 


First disconnect the wire leading from the rheostat to the 
arc lamp, leaving only the wire connected which leads from 
the source of electrical supply to the rheostat. Now, first 
having removed the casing of the rheostat, connect one of 
your test lamp wires to the frame of the rheostat and the 
other test lamp wire to a wire of opposite polarity. Assum¬ 
ing we have disconnected the wire from the left-hand binu- 
ing post, in Fig. 103, we will disconnect coil or grid A, and 
if the test lamp still burns, or if there is still a spark when 
its contact with the rheostat frame is made and broken, we 
know the trouble is not in A, since the ground still exists. 
We therefore connect BCD and E. When coil or grid E 
has been disconnected the test lamp goes out or the spark 
ceases, hence we know the trouble lies in that coil or grid. 
The trouble in coil or grid E may be due to direct connec¬ 
tion with the frame caused by sagging, or it may be and 
probably is due to a fault in the insulation. 

If a rheostat consists of two banks of coils or grids, con¬ 
siderable labor can be saved by disconnecting one bank 
from the other, and then testing each as a whole to find out 
which half the ground is in. It is then only necessary to 
disconnect the individual coils or grids of the defective side. 

GROUNDING THE PROJECTOR.— It is always advisable 
that the projector lamp house, mechanism and frame be per¬ 
manently grounded to the metal of the projection room, if 
any there be, and then the whole may or may not be thor¬ 
oughly grounded permanently to a water pipe. 

The reason for grounding the projector to the projection 
room metal work is that if the projector be insulated from 
the metal of the projection room and the lamp should be¬ 
come grounded to the metal of the lamp house it would 
charge the whole mechanism with voltage, and, should the 
projectionist in the act of putting a reel in the magazine 
touch the reel to the magazine and the metal of the projec¬ 
tion room there would be a spark which might set fire to 
the film. 

There is no real necessity for the grounding of the metal 
of the projection room as a whole. It may or may not be 
done, as best suits the idea of the individual. 

EFFECT OF GROUNDING. —The effect of grounding the 
projector lamp is that current is wasted and the brilliancy 
of the light is itself likely to be affected, particularly if the 
ground be a heavy one, since a portion of the current is 
escaping through the shunt circuit produced by the ground, 


MANAGERS AND PROJECTIONISTS 


36) 


instead of passing through the carbons and producing light, 

Projectionists will do well to test their lamps for ground 
every day. It only takes a few moments and is well worth 
the trouble. 

One prolific source of current leakage in the arc lamp is 
due to carbon dust settling across the insulation of the car¬ 
bon jaws. This is not so likely to happen in the modern 
type of lamp, but with the old lamps it was a constant 
source of annoyance. However, the projectionist will do 
well to dust off the top of his carbon arms, particularly the 
insulation, every day before he starts the run. 


IF YOU DO BETTER 
WORK WHEN THE BOSS 
IS WATCHING, YOU ARE 
A VERY POOR MAN TO 
HAVE ON THE PAY ROLL. 



362 


HANDBOOK OF PROJECTION FOR 


The Projector 

T HE LAMP HOUSE OF THE PROJECTOR has grown 

from a little sheet iron affair about six inches wide by 
twelve inches long and twelve inches high, to an impos¬ 
ing structure of very ample dimensions. It is well that it is so, 
because a roomy, well constructed, well ventilated lamp 
house is essential to high-class work in these days of high 
amperage and a brilliantly lighted screen. 

In the early days when it was the exception to use in ex¬ 
cess of 25 amperes for projection, and 30 was about the 
limit, very little attention was paid to the housing of the 
lamp. The main object was to provide a holder for the 
condenser and to confine at least a part of the light. With 
the modern projection arc, in some instances using as high 
as 120 amperes, the tremendous heat generated has com¬ 
pelled close attention to lamp house ventilation and has 
compelled the increase in size before mentioned, while the 
advance in projection optics and the tendency to breakage 
of lenses through the heat of high power arcs has obliged 
manufacturers to give close attention to the condenser 
mount, all of which has resulted in a vastly improved and 
very efficient lamp house. 

LAMP HOUSE VENTILATION.— The ventilation of the 
lamp house is of extreme importance, especially where high 
amperage is used, since unless there be ample air circulation 
the temperature inside it will reach a very high degree, 
which will automatically operate to (a) reduce the capacity 
of the carbons, (b) injure the wires on the interior of the 
lamp house, as well as to some extent the metal of the car¬ 
bon jaws themselves, (c) set up a tendency to abnormal con¬ 
denser breakage and (d) through heat radiation make it 
both uncomfortable and unhealthful for the projectionist in 
southern climates, or during warm weather in more north¬ 
ern latitudes. 

One cause for poor lamp house ventilation is chargeable 


MANAGERS AND PROJECTIONISTS 


363 


to what can be termed nothing else than pure unadulterated 
carelessness or laziness on the part of the projectionist, 
who allows the vent screens to become clogged either 
almost or quite solid with ash and dirt. 

In the process of volatilization water glass, which forms 
the binder of the core of carbons, produces a gray colored 
ash which is very light in weight. It is this ash which forms 
the white coating found at the top of and on the interior 
walls of the lamp house. It is carried upward by the drait 
and gradually chokes the perforated metal used for vent 
screens in the old style lamp house. Unless this deposit be 
frequently removed and the screens thoroughly cleaned, all 
ventilation will be stopped in a comparatively short time. 
It is the failure to keep these screens free from this accu¬ 
mulation which we have charged to carelessness or laziness 
on the part of the projectionist. We do not like to use such 
harsh terms, but the fact remains that this condition is 
responsible in altogether too many instances where con¬ 
denser breakage is complained of. 

BEST METHOD OF VENTILATION.— The best method 
of ventilation is illustrated in Fig. 104, in which a three or 
four-inch sheet metal pipe is attached to the tcrp of the 
lamp house, and is either carried to the open air or con¬ 
nected to the vent flue. 

Some years ago the 
author secured the 
consent of the leading 
projector manufactur¬ 
ers to the placing in 
the top of their lamp 
house an opening to 
which such a pipe 
could be attached. The 
installation of a vent 
pipe of this kind 
serves to carry away 
very much of the heat 
of the arc, hence re¬ 
duces the liability to 
condenser breakage 
and renders the posi¬ 
tion of the projection¬ 
ist far more tolerable 
during the hot sum- 






















364 


HANDBOOK OF PROJECTION FOR 


mer months. It has the hearty endorsement and ap¬ 
proval of the projection department of Moving Picture 
World and the author of this book. The author would ear¬ 
nestly recommend its installation in all projection rooms, on 
the score of health if there were no other reasons; because 
the pipe carries away all fumes of volatilizing carbons 
which are not especially healthful. In installing the pipe, 
however, remember that only a part of its purpose is 
served if you merely run a short piece, of pipe up a foot or 
so above the lamp house. This ventilates the lamp house 
all right, but it does not remove from the room either the 
heat of the arc nor the gases formed by the volatilizing of 
carbon; also it would not be approved by the authorities in 
some cities. 

Run the pipe out to the open air, into the projection room 
vent flue or into the exhaust pipe if the projection room is 
connected with the house ventilation system. 

It is not necessary that this pipe be capped with a screen 
if this is done, because in any event it would not be less 
than five or six feet long, and by no stretch of even the 
wildest imagination would a spark from an electric arc 
carry such a distance. 

SWING JOINT IN VENT PIPE.— If it is necessary to 
swing the lamp house over to a stereopticon lens it can be 
readily done by providing a combined swing and slip joint 
in the lamp house vent pipe. 

Lack of ample ventilation in the lamp house causes ex¬ 
hibitors as a whole a large sum in condenser breakage 
every day. While no figures are available we believe this 
item will in all probability amount to as much as $500 a 
day in the United States and Canada alone, meaning that 
that value in condenser lenses probably is destroyed which 
would not be destroyed if lamp houses all had ample ventila¬ 
tion. 

PROJECTING CRATER IMAGE. —As has already been 
pointed oht, from many viewpoints, it is desirable to pro¬ 
ject an image of the crater to the wall, ceiling, floor or to 
some other place where it will be constantly in view of the 
projectionists. A crater projector designed to be attached 
to the lamp house door may be purchased from almost any 
dealer in supplies, or one may be made as per directions 
given under “Crater Angle,” Page 405. 


MANAGERS AND PROJECTIONISTS 


365 


LIGHTING INTERIOR OF LAMP HOUSE.— It would be 
a very simple matter to place a small porcelain lamp recep¬ 
tacle in the bottom of the lamp house, at the right hand, . 
rear corner. From one side run a wire to one side of any 
convenient incandescent circuit. From the other side at¬ 
tach to the other side of the circuit through a spring- 
switch, made as per Fig. 105, attached to the right hand 
lamp house wall in such way that a piece of fibre fastened 
to the lamp house door will shove the switch open, thus 
putting out the light, when the lamp house door is closed. 

By the use of a low C-P lamp the interior of the lamp 
house is thus automatically illuminated when one opens the 
door to re-set the carbons, etc. 

CONDENSER HOLDER— It is only of late years that 

any particular atten¬ 
tion has been paid to 
the condenser holder, 
but now all the recog¬ 
nized professional pro¬ 
jectors have a more 
or less efficient ar¬ 
rangement both for 
holding the lenses, and 
for spacing them 
properly with relation 
to their distance from 
each other. A con¬ 
denser holder which 
has no provision by 
means of which the projectionist may alter the spacing of the 
lenses by means of an adjusting screw located outside the 
lamp house and casing is not a good holder. 

WHY CONDENSERS BREAK. —Condenser lenses break 
because one part of the lens, the edge, is thin, and another 
part, the center, is thick, hence when subjected to heat the 
thin edge increases in temperature very rapidly and expands 
very rapidly as compared to its thick center. Also when 
the arc is shut off the thin edge contracts very rapidly as 
compared to the thick center. 

We believe it was W. G. Woods, a San Francisco projec¬ 
tionist, who first recognized this proposition and undertook 
to provide a means for equalizing the contraction and ex¬ 
pansion as between the thin edge and the thick center of 
the condenser lenses. The idea, which has later been 








366 


HANDBOOK OF PROJECTION FOR 


adopted in one form or another by all manufacturers of pro¬ 
fessional projectors, was to firmly clamp the thin edge of 
the lens in a metal retainer, the amount and kind of metal 
of which was carefully calculated with a view of its tem¬ 
perature rising as nearly as possible equally with the tem¬ 
perature of the thick center of the lens, and since the thin 
edge would be clamped in this metal ring, radiation would 
prevent it from heating faster than the metal holder, and 
the whole lens would thus be brought up to temperature 



Figure 106. 


evenly, and by reversal of the process would lose its tem¬ 
perature evenly when the arc is shut off. 

The first of these holders, known as the “Elbert Holder,” 
is shown in Fig. 106. It was the holder designed for the 
Powers projector by Mr. Woods, who also designed holders 
for the Simplex and the Motiograph. These holders are, so 
far as we know, no longer marketed. 

PREDDY HOLDER. —Walter Preddy of San Francisco 
still makes the Preddy condenser holder illustrated in Fig. 
107. 




MANAGERS AND PROJECTIONISTS 


367 


This holder is excellent for use with old style lamp houses 
which are not equipped with the modern condenser holders 
now put out with all professional projectors. They are 
moderate in price and may be had from any first-class sup¬ 
ply dealer, or from Walter Preddy, San Francisco, Cali¬ 
fornia. Their method of mounting is shown at the right in 
Fig. 107. 

REQUIREMENTS OF CONDENSER HOLDER.—The 

requirements of the modern condenser holder are that the 
metal of the holder shall have good, even contact with 
lenses, since unevenness of contact between the metal and 



Figure 107. 


the glass produces uneven radiation, with uneven expansion 
and contraction, and consequent tendency to breakage. It 
must grasp the lens firmly enough to insure good contact 
between the metal and the glass, with consequent evenness 
of radiation, but at the same time not in any way binding 
the lens, because the ratio of expansion of glass and metal 
is different, and if the lens be bound tightly in the holder, 
expansion will exert such a tremendous force that breakage 
will almost inevitably occur. The metal in which the lens 
rests must be so calculated with regard to its amount that 
the purposes of a heat and cold reservoir as hereinbefore 
set forth will be as nearly as possible perfectly served. The 















368 


HANDBOOK OF PROJECTION FOR 


holder must be so constructed that by means of an adjust¬ 
ing screw located outside the lamp house the projectionist 
may alter the distance between the two lens holders in or¬ 
der to accommodate the difference in thickness of lenses of 
different focal length. The holder must be so constructed 
that while it is held locked securely in place, the lenses 
may still be made immediately and easily accessible to the 
projectionist for removal and replacement, always remem¬ 
bering that removal and replacement in a minimum of time 
may be necessary when the lens to be removed is very 
hot, and a hot lens is a reasonably difficult thing to handle. 

POSITION OF CONDENSER HOLDER.— The modern 
and generally accepted practice is to place the condenser 
holder inside the lamp house, where the lenses are sub¬ 
jected to a rather high but comparatively even temperature, 
rather than to the uncertain and possibly rather sudden 
changing temperature of the condenser casing located out¬ 
side the lamp house. 

SHUTTER FOR CONDENSER.— Some modern lamp 
houses are provided with an interior douser, which comes 
down between the arc and the collector lens, rather than in 
front of the converging lens. This is, we believe, good 
practice, since it to a considerable extent protects the col¬ 
lector lens from sudden changes of temperature when the 
lamp house door is opened while the lenses are hot. 
Such a shutter may be installed by the projectionist him¬ 
self, and may be so made that it will be lowered by the act 
of opening the lamp house door and raised by the act of 
closing it, so that the lens will always be protected when 
the lamp house door is open. In order to do this a shutter, 
preferably made of quarter-inch asbestos millboard, must 
be installed in grooves, the latter so supported that when 
the shutter rests on the bottom stop it will cover the in¬ 
terior surface of the condenser. From the top of this shut¬ 
ter a light chain may be run up and out through a small 
hole drilled in the lamp house roof or wall, and after pass¬ 
ing over a pulley be attached to an arm riveted to the lamp 
house door in such way that opening the door will drop 
the shutter, while closing the door will pull it up. We 
believe this description is sufficiently clear to serve the pur¬ 
pose without the aid of an illustration. 

KEEP THE LAMP HOUSE CLEAN.— The careful, com¬ 
petent projectionist will keep his lamp house scrupulously 
clean. It is not creditable to the projectionist to find dirt, 


MANAGERS AND PROJECTIONISTS 


369 


dust, pieces of broken carbons, carbon stubs, etcetera, lit¬ 
tering the floor of the lamp house. It doesn’t impress one 
with the idea that the man in charge is a good workman, 
because it is not a workmanlike way of doing things. 

At least once a week the projectionist should, using a 
good hand bellows, blow the carbon ash out of the vent 
screens down into the lamp house, whence it Can be re¬ 
moved. Of course if the lamp house be equipped with a 
vent pipe, as before described, this will not be necessary, 
though the carbon ash should be swept out of the top of the 
lamp house once a week, merely as a matter of cleanliness. 
The removal of this ash is rather an unpleasant job, because 
being very light in weight it is apt to fly all over everything. 
Our own way of doing the thing used to be to take the lamp 
house off once a week, take it outside and clean it thorough¬ 
ly, but this is hardly practical with large, heavy modern 
lamp houses. By blowing the dust down into the lamp 
house first, however, and by careful work thereafter, very 
little, if any, of it should escape into the room. Lamp 
houses should have an opening at the bottom through 
which dust and dirt can be swept. The removal of dirt from 
the bottom of a lamp house not thus equipped is a tedious 
and a decidedly unpleasant task. 

Many projectionists who are using old type lamp houses 
will find that when the lamp has the desired angle, the 
lower carbon jaw will come into contact with the front 
wall of the lamp house, thus charging the whole projector 
with EMF. Where this occurs the projectionist should 
secure a thin piece of asbestos millboard (sheet asbestos 
will do), and attach it to the front wall of the lamp house 
in such way that it will come between the lower carbon jaw 
and the metal of the lamp house. 

If the lamp house is of the old, unlined, narrow type it is 
an excellent plan to rivet l/8th-inch asbestos millboard, or 
sheet asbestos, to the left hand wall or door opposite the 
binding posts of the lamp, since many annoying grounds 
are caused by a stray strand or strands of the lamp leads 
protruding and making electrical contact with the lamp 
house wall. 

THE LAMP— The projector arc lamp is a most impor¬ 
tant feature in the production of good projection light. It is 
in fact impossible to secure consistently even screen illumi¬ 
nation with a poor, badly worn, loose, “wabbly” or dry lamp. 
Theatre managers who oblige their projectionists to work 


370 


HANDBOOK OF PROJECTION FOR 


with an old style arc lamp are doing a very foolish thing, 
and one which cannot but result in inefficient work on the 
screen. 

To be in accord with modern practice a projector lamp 
must have an adjustment for feeding the carbons; an ad¬ 
justment by means of which one or the other of the carbon 
jaw may 'be moved sidewise; an adjustment by means of 
which the whole lamp may be moved forward and back; an 
adjustment by means of which the whole lamp may be 
raised vertically up or down; an adjustment by means of 
which one or the other, preferably the lower, carbon jaw 
may be moved forward or back with relation to the other 
jaw; an adjustment by means of which the whole lamp may 
be moved sidewise; and an adjustment for altering the angle 
of the lamp as a whole. All these adjustments, except the 
last named, must be available to the projectionist from the 
exterior of the lamp house. In addition to this many pro¬ 
jectionists demand that there be means provided for the 
tilting of the carbon jaws to accommodate the “jack-knife” 
carbon set, but the author believes that just as good, if not 
better results would be had if this last adjustment were 
entirely omitted. 

INSULATION. —The carbon jaws must of course be in¬ 
sulated from the carbon arm, the jaws being the only part 
of the lamp electrically charged. This insulation is com¬ 
posed of sheets of mica, and there is of course an insulating 
“barrel” of mica around the screws or bolts which clamp 
the jaw to the lamp arm. Projectionists should be very 
cautious about loosening the joint between carbon arm and 
jaw, because if the insulation around the bolts or screws be 
injured or destroyed considerable trouble is likely to be 
experienced in replacing it. 

CARBON DUST GROUNDS. —The projectionist should 
be careful to keep the lamp free from carbon dust, partic¬ 
ularly around the insulation, since it is quite possible to 
form a current-carrying ground through carbon dust set¬ 
tling on the top of the surface of the carbon jaws and arms. 
Before projector manufacturers adopted the practice of 
raising the edge of the mica insulation above the surface of 
the metal at the top of the carbon arm and jaw, carbon 
dust formed a prolific source of grounds in the lamp. This 
can no longer occur unless the projectionist is careless 
enough to allow a very considerable amount of dust to 
accumulate. 


MANAGERS AND PROJECTIONISTS 


371 


CARBON CLAMPS. —It is of very great importance that 
the carbon jaw make as nearly as possible perfect electri¬ 
cal contact with the carbon, since otherwise heat will be 
generated; also there will be more or less arcing between 
the carbon and the metal, which will tend to gradually 
roughen the jaw by forming pit-holes in its surface, thus 
setting up a very bad condition indeed. Any heat caused 
by poor contact between the metal and the carbon increases 
tendency to penciling of the carbon, because it adds to the 
heat of the arc the heat formed by the poor contact. A 
good plan for keeping the contact in good condition is to 
wrap a round piece of wood about the diameter of the car¬ 
bons being used with No. 00 sand paper, or very fine emery 
paper or cloth, and every day before starting the run clamp 
this lightly into the carbon jaws and give it a few twists. 
This will remove any scale or other thing adhering to the 
carbon Jaws which might tend to increase the resistance 
between the metal and the carbon. The cleaner above de¬ 
scribed is easily made by cutting sheets of sand or emery 
paper into strips an inch or so wide, and winding them 
spirally around the cleaning rod tightly, fastening the up¬ 
per end with a thumb tack such as draughtsmen use. 

LAMP LUBRICATION is an exceedingly important thing. 
Projectionists should make it their practice to lubricate 
their lamp thoroughly at stated periods. Twice a year all 
screws should be removed from the lamp, dipped in kero¬ 
sene and then into a box of powdered graphite, the oil 
merely being intended as a binder to hold the graphite to 
the screw until it can be replaced. Moving parts should be 
lubricated by rubbing them with a cloth wet with kerosene 
and then with graphite. If kerosene is not available lubri¬ 
cating oil may be used as a binder for the graphite, but it 
must be remembered that the oil is not intended as a lubri¬ 
cant, but merely as a medium to hold the graphite to the 
metal until it is thoroughly coated. The graphite itself is 
the lubricant, graphite being in itself a high-grade lubri¬ 
cant and one which is impervious to the action of heat at 
ordinary temperature. In reassembling the lamp, remember 
that the greater the amount of graphite adhering to screws 
and moving parts the better. If you have never done this 
you will be astonished at what a difference it will make in 
the handling of the lamp. 

Make it your invariable practice to remove the carbon 
clamp screws every day if the run be a twelve-hour one, or 


372 


HANDBOOK OF PROJECTION FOR 


in any event frequently, and lubricate them with graphite 
as above set forth. Do this and you will not need to twist 
up the screws with a plier. In fact, if you have been using 
unlubricated carbon clamp screws you will be very likely 
to crush the first few carbons you put in. 

ASBESTOS WIRE LAMP LEADS.— The asbestos wire 
lamp leads are a thing concerning which the projectionist 
must use care and intelligence, else he will have heavy loss 
by reason of their high resistance. 

ARC CONTROLLERS. —There are now on the market 
several arc controllers designed to automatically feed the 
carbons. The use of these controllers cannot be too highly 
recommended, since they maintain an absolutely steady arc 
length, hence an absolutely steady screen illumination, al¬ 
ways of course provided they are proprely adjusted and 
handled by the projectionist. 

The hand-fed lamp never has and never will give as 
steady screen illumination as that provided by a good arc 
controller. The principal upon which most arc- controllers 
operate is as follows: 

Every change of arc length means a change in arc voltage. 
When the arc is burning with a given carbon separation 
there is a certain difference of potential between the car¬ 
bons called “arc voltage.” As the carbons burn away the 
distance between their tips is of course increased, which 
means that the resistance of the arc is increased, hence a 
higher voltage is necessary to force the current across the 
gap. In other words added distance between the carbon 
tips raises the arc voltage automatically. Automatic arc 
controllers make use of this fact and depend upon it for 
their action. When the carbon burns away sufficiently 
to alter the arc voltage by a very small amount, a mechan¬ 
ism is engaged which feeds the carbons together until the 
normal arc voltage is reestablished, whereupon the mech¬ 
anism automatically ceases to function until the arc voltage 
again rises sufficiently to re-energize it. 

A good arc controller operates on such slight change in 
carbon separation distance that the feeding of the carbons 
is well nigh imperceptible, hence a practically uniform dis¬ 
tance of carbon separation is automatically maintained. We 
will present herewith, in proper place, an illustration of 
some arc controllers now on the market, at the same time 
describing their characteristics as set forth by their manu¬ 
facturer. We do not deem it advisable to undertake the 


MANAGERS AND PROJECTIONISTS 


373 


giving of greatly detailed instructions on this class of equip¬ 
ment, because such instructions should accompany them 
when they are installed, and there is constant liability to 
slight changes in construction which would greatly lessen 
the value of detailed instructions were we to provide them. 
See Page 559. 


KNOWLEDGE IS 
POWER. 



374 


HANDBOOK OF PROJECTION FOR 


Carbons 


IGHT is the foundation of projection, and light for 



projection purposes depends to a very great extent 


for its steadiness, its brilliancy and tone, upon the 
arc lamp electrodes (carbons), since practically the entire 
available illumination is produced by the incandescence of 
the floor of the “crater” formed by the current action on 
the tip of one (the positive) of the carbons if D-C is used, 
because one carbon is then constantly positive, or of both 
carbons if A-C is used at the arc, since then both carbons 
are alternately positive and negative. 

Each form of arc lighting requires the use of carbons 
having different physical characteristics. For projection 
work, where the light must be, to all intents and purposes, 
•absolutely steady in value, not too harsh in tone, and very 
brilliant, a special grade of carbon is required, which must 
be very free from impurities, hard spots and other imper¬ 
fections. Such carbons call for very great care in manu¬ 
facture, and a high degree of engineering skill in the prep¬ 
aration of formulas. 

HOW THEY ARE MADE. —The procedure of American 
carbon manufacturers in the making of projection carbons 
is as follows: The basis of projection carbon is lampblack, 
the purest form of carbon known. The ordinary lampblack 
used in the manufacture of other types of lighting carbons 
contains far too much ash to be satisfactory, therefore a 
specially selected black is employed. Even this material 
contains considerable volatile matter, which is driven off by 
calcination at a high temperature. This calcined material 
is known as “carbon flour,” and is so pure that it is less than 
one-twentieth of 1 per cent. (.0005) ash, and contains little 
or no volatile matter. A high grade binder is then added 
to this flour, after which it is machine-mixed into a stiff 
mass, in a fashion very similar to that employed in knead¬ 
ing bread dough. This mass is then fed into the cylinders 
of hydraulic presses, which force it through suitable dies 
under very heavy pressure. As it comes from the presses 
the carbon is received upon grooved boards, made for the 
purpose. It is now in the form of rods. Carbons which are 


MANAGERS AND PROJECTIONISTS 


375 


to be cored are forced with a central hole throughout their 
length, formed by having a steel pin fixed in the center of 
the hole in the die. At the end of the process just described 
the carbons are ready for baking. The form of the binder 
contained in the green carbon must be changed by driving 
off the volatile matter therein contained and depositing the 
residue throughout the electrode in the form of pure car¬ 
bon. Inasmuch as the quality of the finished carbon de¬ 
pends to a large extent upon the method and temperature of 
the baking, this is one of the most important operations in 
its manufacture. The green carbons are first packed in 
special cylinders, to keep them from becoming crooked and 
to protect them from injury. They are then placed in gas 
fired furnaces, specially designed to secure uniform heating, 
from which air is- excluded during the process of baking. 
The total operation of packing, baking, cooling and unpack¬ 
ing consumes from three weeks to a month. 

After removal from the furnace the carbons are cut to 
proper length and sorted for straightness. Owing to varia¬ 
tion in shrinkage during the baking process, some deviation 
from perfect straightness must be expected. The solid and 
hollow carbons are now separated. The former are taken 
directly to the pointing machine, after which they are 
ready for shipment; the latter go to the coring department. 
Here the central hole in the carbon is filled with the core 
material, which is a non-flaming, arc-supporting substance. 
The core material is mixed into a paste with water glass, a 
soluble alkaline silicate which becomes solid when dried. It 
is then forced into the hole, after which the carbons are re¬ 
baked for a short time at a comparatively low temperature 
in order to solidify the cores, which operation completes 
the process of manufacture. 

PURPOSE OF THE CORE. —In order to understand the 
reason why it is necessary to place a core in carbons used 
for the positive electrode of a projection arc lamp, we must 
first understand a few of the whys and wherefores of the 
arc itself. 

One may close the projector table switch, thus charging 
the carbons with EMF, and bring the carbon tips within 
1 /64th of an inch of each other without results of any kind. 
So long as there is an air gap between the carbons, no mat¬ 
ter how small it may be, neither 110 nor 220 volt current will 
jump the space. Yet when the carbon tips are brought into 
actual physical contact with each other, and current flow is 


376 


HANDBOOK OF PROJECTION FOR 


thus started, the carbons may be separated and the current 
will continue to flow, even after the distance of separation 
has increased to as much as three-eighths or half an inch, 
and under some circumstances even a very much greater 
distance. The novice usually is puzzled to account for this 
phenomenon, the explanation of which is simple. 

Current of the voltage used for projection will not jump 
an air gap of any width at all, but when the carbons are 
brought into contact and separated, at the instant of separa¬ 
tion the action of the current heats the carbon particles to 
the point of volatilization, and in the process of volatiliza¬ 
tion a gas is formed which to considerable extent is a con¬ 
ductor of electricity. From the instant the carbons are 
separated until they are separated so far that the resistance 
of the gas stream is too high to allow of the EMF forcing 
the current across the gap, this gas exists between the car¬ 
bon tips, and furnishes a conductor for the current. 

With this in mind let us examine into the reason for the 
placing of the core in the positive carbon. Electric current 
always seeks the path of least resistance, and where sev¬ 
eral paths are available a very slight change in resistance 
may alter the path of the current. Were we to attempt to 
use a solid positive carbon a crater would be formed the 
same as with a cored carbon, but since it would be utterly 
impossible to secure a carbon mass which would always 
have the path of least resistance in one spot, the center of 
the crater, the main flow of the current would, seeking the 
path of least resistance, move around over the face of the 
crater wherever at any given instant of time the least re¬ 
sistance was offered to its passage, which of course, since 
the light for projection must be absolutely steady, would 
not do at all. 

At the incandescent crater floor the core supplies a far 
greater volume of arc supporting gas than does the material 
composing the surrounding shell, or wall of the carbon, 
hence the current, seeking the path of least resistance, is 
led by the relatively heavier gas volume to the core of the 
carbon, and by the above described condition is kept there, 
which has the practical effect of maintaining the center of 
the crater at the core, with resultant steadiness of illumina¬ 
tion at the plane of the collector lens. 

The reason why only one cored carbon is necessary with 
direct current, and two with alternating, is that with direct 
current only one crater is formed, whereas with alternat- 


MANAGERS AND PROJECTIONISTS 


377 


ing current both carbons are alternately positive and nega¬ 
tive, so that there is actually a crater on both the upper and 
the lower carbon. 

SOLID VERSUS CORED. —The objection to the use of a 
solid lower negative carbon for direct current is that great¬ 
er care is required in order to maintain a steady arc. 

The objection to the use of a cored lower carbon with 
direct current is that, while it makes the work easier for 
the projectionist, where a hand-fed lamp is used, because 
of the fact that the carbons will not need such frequent 
feeding, this is only true by reason of the increased volume 
of gas emanating from the lower core, and this gas forms a 
sort of curtain in front of the positive crater, which 
materially diminishes the illumination supplied to the lens. 

There are those, however, who maintain that, while this 
is true, the gas has the effect of softening the light tone, 
hence it is worth the waste involved. This is to some extent 
true, but we nevertheless hold there are better and more 
economical ways of accomplishing the softening of light 
tones. 

In this connection there are two special negatives or 
lower carbons on the market which should have mention, 
viz.: The Silver tip, made by the National Carbon Com¬ 
pany, and the “Hold-Ark,” made by the Speer Carbon Com¬ 
pany. These are both excellent lower carbons, though both 
have minor objections. The metal plated carbons to some 
extent, have a tendency to pit the collector lens. This is 
caused by the burning away of the metal coating, which is 
sometimes thrown upon the face of the condenser, where 
the incandescent metal burns a spot on the polished surface. 
This trouble has, however, to a large extent, been overcome 
by the manufacturers. 

The Hold-Ark negative has a core, and while this core has 
a reduced gas volume, still the fact remains that it does to 
some extent produce gas, which forms a curtain in front of 
the crater as already explained. 

Notwithstanding these facts, we can recommend botn 
these negatives to projectionists as being decidedly better 
than either the plain solid or plain cored carbon for nega¬ 
tive. 

CARBON SIZE. —The diameter of carbons is a matter of 
very great importance to the projectionist who desires to 
do his work efficiently, and to get the greatest possible 
amount of projection light per watt of current consumed. 


378 


HANDBOOK OF PROJECTION FOR 


If the carbon be too small there will be “penciling” or 
“needling,” which means the burning of the carbon tip to a 
more or less long, slim point. The practical effect of this, 
for very obvious reasons, is to reduce crater area. 

If, on the other hand the carbon be too large, then it 
seems certain that the comparatively large mass of relative¬ 
ly cool carbon lying close to the floor of the crater will, at 
least, to some extent, operate to lower the average crater 
temperature, which must inevitably reduce its candle power 
per unit of area. It therefore follows that carbons either 
too small or too large for the amperage used are not 
efficient. 

INTRINSIC BRILLIANCY OF CRATER.— In the “Elec¬ 
trician,” Volume 32, Pages 117, 145, 169, year 1893, Blondell 
says that although the maximum brilliancy of the crater is 
independent of the current flowing in the arc, yet the aver¬ 
age brilliancy of the incandescent portions of the crater in¬ 
creases, both with intensity and density of current, until the 
crater is well saturated. “If,” he continues, “the volume of 
the current be suddenly altered, the intrinsic brilliancy 
undergoes a temporary but very appreciable variation, 
which may reach ten per cent, but which diminishes gradu¬ 
ally until the dimensions of the crater are so altered as to 
restore the surface to the value it ought to have for the 
new current.” 

Blondell says that the heating of the crater only takes 
place at the surface, and that the temperature of volatili¬ 
zation is only reached by a very thin, superficial layer, all 
of which seems to make plausible our argument that a 
comparatively large body of relatively cool carbon near 
the floor of the crater would operate to decrease crater 
brilliancy. 

In the projection department of the Moving Picture 
World, March 15, 1919, issue, Mr. G. F. Binkelman, of the 
engineering force of the Speer Carbon Company, gave a 
very interesting and instructive talk on carbons, from which 
we have extracted the following data. 

The charts and diagrams were all supplied by the Speer 
Carbon Company, to whom we owe thanks for their being 
made available. 

Fig. 108 is a diagrammatic representation of the carbon 
set used for the experiments from which the data was ob¬ 
tained. It will be observed that all measurements were 
made with an ll/32d-inch space between carbon tips—an 


MANAGERS AND PROJECTIONISTS 379 

ll/32d-inch arc length. Hold-Ark negatives were used in 
all tests, but two well-known makes of carbons in very 
general use were used for positives. The test plate was ten 
inches from the crater and the crater maintained at a 45 
degree angle with what would be the optical axis were we 
dealing with a projector, lens system. The carbons were 
inclined 15 degrees from the perpendicular. In fact every¬ 
thing was as it should be for a reliable test of the matters 
it was sought to determine, except that the crater angle 
was not at its point of greatest efficiency. This would not, 
however, affect the value of the results, but let it be remem¬ 
bered that in these tests we are not considering the lens sys¬ 
tem at all, but merely the light given off by the projection 
arc crater as a whole. 



Figure 108. 

(10 X 10 ft. = 100 sq. ft. = Distance squared, (Slide Constant 11.5) W) 


In Fig. 109 we have curves showing the relation of candle 
power to amperage; it will be observed that for a given size 
carbon the increase in candle power is exactly proportional 
to increase in amperage. In other words, the curve is a 
straight line. It will also be observed that at any given cur¬ 
rent strength less than the capacity of any of the three 
sizes of carbons used the candle power per ampere de¬ 
creases as the diameter of the carbon is increased. For in¬ 
stance: Taking the fifty ampere line, Fig. 109, the % carbon 
gives a trifle less than 7,000 candle power, the 54 carbon a 
trifle less than 8,200 candle power and the 54 gives 9,400 
candle power. Or, taking the 8,000 candle power line we 
find that the 54 carbon gives that candle power at a bit 
less than 55 amperes, the 54 at a bit less than 50 amperes 













380 


HANDBOOK OF PROJECTION FOR 


and the % at a bit less than 55 amperes. We also see that 
this difference holds good clear up to the capacity of the 34 
and 34 carbons, which does not seem quite right. The dif¬ 
ference should, it seems to us, decrease as the current ap¬ 
proaches more nearly a carbon capacity. 

We learn from this that if we use a 34 carbon for amper¬ 
age within the capacity of a 34 carbon we will be wasting 
almost exactly five amperes of current, and if we use a % 
where a 34 is large enough we waste the same amount, 
whereas when we use a % where a 34 is large enough we 
waste ten amperes, which, if we take current through rheo¬ 



stats from a 110 volt line, will mean 1,100 watts of energy 
wasted. 

Mr. Binkelman attributes the difference to the fact that 
the larger carbon has a larger radiating area and a greater 
cross-sectional area, hence more heat is radiated away from 
the crater, with result that its temperature is reduced, in 
which view we hold him to be entirely correct. It is but 
another way of saying that the comparatively large amount 
and comparatively cool carbon near the crater floor reduces 
the temperature of the floor. 

Fig. 110 is the same as Fig. 109, except that a different 
make of carbon was used. It will be noted that the differ- 


















































































MANAGERS AND PROJECTIONISTS 


381 


ence in candle power per ampere is greater with this kind 
of carbon, also there is a slight variation when we compare 
the difference between the $4 and Y and the Y\ and 
Why this is we are unable to say positively, but it surely 
must be due to peculiarity of either the $4 or the 7/% carbons 
used for the test. The fact remains, however, that different 
makes of carbon evidently do make for somewhat different 
results when over-size carbons are used. 



Figure 110. 


In Fig. Ill the curves (in charts of this kind the lines are 
called “curves,” even though they be straight lines) show 
that crater area increases exactly in proportion to increase 
in amperage when we consider a carbon of given size, but 
that the crater area for a given amperage increases as 
carbon size is increased. It is curious that according to 
this chart this holds exactly true regardless of how much 
the carbon may be under-loaded. For instance, we see, 
Chart A, Fig. Ill, that at forty-five amperes the craters of 
s/s, Y and 7/% carbons are respectively (roughly) .13, .16 and 
.18 of a square inch. Referring back to Fig. 110 we find that 
the $4 carbon has a greater total light giving power for a 














































































































































382 


HANDBOOK OF PROJECTION FOR 


given amperage than the % or ^ carbon. We thus arrive 
at the inevitable conclusion that: 

Crater area per ampere is greater with the larger carbon, 
but the light giving power per unit of crater area decreases 
as carbon size is increased. 

Concerning this Mr. Binkelman says: “Let it be under¬ 
stood, however, that the amount of light, or intrinsic bril¬ 
liancy per unit crater area should be very nearly equal for 



Am peres 


Figure 111. 


















































































































































































































































































































































































MANAGERS AND PROJECTIONISTS 383 

the different size carbons when the craters are well satu¬ 
rated.” 

By “saturated” it is meant when the carbon is working 
close to its normal capacity. In this view we concur, though 
it seems to be to some extent contradicted by the charts in 
Fig. Ill, especially in Chart A. 

Fig. 112 is an efficiency chart. In some respects it is not 
quite as understandable as we would like it to be, but one fact 
stands out clearly, viz.: taking sixty-five amperes, for ex- 



Figure 112. 


ample, we find that whereas with a five-eighths carbon it 
requires about .29 watts to produce one candle power, with 
a three-quarters carbon something more than .32 watts are 
required and with a seven-eighths carbon just .36 watts are 
necessary. The waste in under-loaded carbons is thus 
again made apparent, since a waste of .03 watt per candle 
power would mean 480 watts waste in a 16,000 candle power 
arc. 

From the experiments Mr. Binkelman concludes that the 
most efficient point at which to burn carbons is just below 

































































































































384 


HANDBOOK OF PROJECTION FOR 


the point where the crater is completely saturated, beyond 
which point penciling is set up. 

In Fig. 113 we see the effect of “penciling” or “needling” 
of carbons, which occurs when the carbon is working above 
its maximum capacity. 

Note: Penciling may begin at a point far below the nor¬ 
mal capacity of a carbon, when conditions, such as poor 
contact or abnormal temperature inside the lamphouse, act 
to reduce its capacity by adding to the temperature caused 
by ordinary current action. 



Figure 113. 

In Fig. 114 we get a glimpse of the effect of amperage on 
crater shape and area, remembering that in the picture the 
actual size is greatly reduced. Actual crater size may be 
determined by increasing the dimensions of the crater as 
many times as it is necessary to increase the diameter of 
the carbon in the picture to make it the actual measurement 
of the carbon itself. The craters are for two grades, or 
makes of carbon, designated as “Grade A” and “Grade B." 

The rule is therefore established that the practical operat¬ 
ing point of greatest efficiency is a point five amperes below 
the penciling point of any given carbon. 




MANAGERS AND PROJECTIONISTS 


385 




Ampere s 


Oia, 

Amperes 


35 




Grade 5 ,Cfi rb'ons 


Amperes 57 


Figure 114, 










386 


HANDBOOK OF PROJECTION FOR 


Either above or below the penciling point efficiency falls 
off, and five amperes below penciling is as close as it is 
practical for the projectionist to approach the actual capac¬ 
ity of the carbon. This means, however, that the projec¬ 
tionist must himself determine the penciling point of any 
given lot of carbons, since not only will the penciling point 
vary with different makes of carbon, but also to some ex¬ 
tent with different lots of the same brand. 

Determining the penciling point is a simple matter, since 
the projectionist has but to install a set of the new carbons 
and gradually increase amperage until penciling starts, 
whereupon five amperes less current will be the correct 
operating point for that particular lot of carbons, as nearly 
as it is practical to determine it. 

Mr. Binkelman says : “To give Grades A and B a rating 
in amperes would result about as follows : 55 to 60 amperes 
use carbons ; 75 to 80 use 34 carbons, and between 90 and 
95 amperes use % carbons.” 

It will, however, be noted that this leaves gaps of con¬ 
siderable amount, and in any event it could be only ap¬ 
proximately correct. On the other hand, Mr. Binkelman 
has made about the only suggestion available in practice, 
because of the limitation in carbon sizes. 

We need carbons the diameter of which progress by six¬ 
teenths of an inch instead of eighths, but they will not be 
available until projectionists evince sufficient interest in 
efficient work to demand them. 

The whole matter may be summarized roughly as fol¬ 
lows : (a) candle power is directly proportional to current, 
up to maximum capacity of a carbon; (b) decreases with 
increasing carbon diameter, at a given current; (c) maximum 
efficiency is had only when a carbon works just below its 
maximum capacity—its penciling point; (d) crater area is 
directly proportional to current for a given size carbon, and 
increases with carbon size at the same current (see further 
comment, Page 381); (e) arc voltage increases directly in 

proportion to current increases; (f) quantity of carbon 
(cubic inches) consumed varies directly with current, and is 
independent of carbon size at any given current. 

The foregoing constitutes a valuable discussion of the 
various points treated, both from the theoretical and the 
practical viewpoint. As applied to practice it all sums up in 
the proposition that the projectionist, having first selected 
the brand of carbon he proposes to use, should make tests 


MANAGERS AND PROJECTIONISTS 


38/ 


of various sizes and determine which size will come nearest 
to burning at five amperes under the penciling point at the 
amperage he desires to use. 

If carbon companies put out tables suggesting the amper¬ 
age their carbons are to be used at it should be dis¬ 
tinctly stated thereOn that the amperage given for the 
various sizes is the nearest practical approach to five am¬ 
peres bdow the penciling point. 

INSPECTION. —The projectionist should carefully examine 
each bundle of carbons before using. Cracks running length¬ 
wise of the carbons are in a way characteristic of the 
product, and do no harm. They are caused by slight error 
in the consistency of the paste from which they are formed. 
Chip cracks running around the circumference, however, 
condemn the carbons, since there would be a tendency to 
break off at this point, though hair cracks are often found 
running around the circumference of good carbons. They 
are due to the same cause as the longitudinal cracks, and 
are of no consequence. 

EXAMINE CORES. —The ends of cored carbons should be 
carefully examined, and if too many of them show indica¬ 
tion of imperfection in the core they should be rejected. It 
is absolutely essential to high class work on the screen that 
all cores be thoroughly continuous, also that the core 
adhere to the wall of the carbon sufficiently well to prevent 
short sections of it dropping out as the carbon is consumed. 
Carbon with a section of its core lacking is one of the most 
annoying things the projectionist is called upon to deal with. 
Absence of the core not only produces unsteadiness in the 
light while that section of the carbon is being burned away, 
but also alters the tone of the light, and if the center of the 
crater is in focus at or near the film plane, the absence of 
the core will produce a dark spot at the center of the screen. 

HARD SPOTS in the carbon due to faults in manufacture 
were of very common occurrence in the early days of pro¬ 
jection, and were a source of great annoyance to the pro¬ 
jectionist. Such spots are believed to be caused by the 
lack of thorough mixing of the carbon dough in the early 
stage of manufacture. They are, however, now so seldom 
encountered that they may be said to have been to all 
intents and purposes eliminated. 

HARD AND SOFT CARBONS. —Some carbons which are 
too hard have a tendency to produec yellow light through 
faulty cratering and slow burning, with resultant short arc 


388 


HANDBOOK OF PROJECTION FOR 


and increased tendency to interference by the lower carbon 
tip. All these things result in an unsteady light of relatively 
low intensity. On the other hand, carbons which are too 
soft burn away rapidly, hence are not economical, though 
they usually provide good illumination while they last. 

CARE OF CARBONS. —It is essential to good results on 
the screen that the projection carbons be thoroughly dry. 
Carbons should, therefore, not only be stored in a dry place, 

but thorough 
dryness should 
be further in¬ 
sured by mild 
heating for a 
day or two be¬ 
fore using. This 
latter may be 
accomplished 
by attaching a 
pair of hooks 
to the lamp 
house as indi¬ 
cated in Fig. 
115, but it is 
recommended 
that projector 
manufacturers 
provide some 
sort of carbon 
receptacle 
either in or on 
Figure 115. the top of t h e 

lamp house, 

capable of containing from six to a dozen carbons, both 
negative and positive. 

BURNING CARBON STUBS. —Modern projection lamps 
accommodate 6 inch lower and 12 inch upper carbons, but it 
it is not always practical, particularly where 2,000 foot reels 
are used, to burn carbon stubs very short in the regular 
way. 

There are now on the market any number of “carbon 
economizers” which are nothing more nor less than a metal 
shank at the top of which is a receptacle in which the car¬ 
bon stub is clamped by means of a suitable mechanism. 
This arrangement clamps in the regular lamp carbon jaw and 








MANAGERS AND PROJECTIONISTS 


389 


allows of the carbon stubs being burned down until only an 
inch or two remains. They may be had of any supply dealer. 

EQUIVALENTS. —The equivalent of millimeters in frac¬ 
tions of an inch will be found on Page 906. 

ALTERNATING CURRENT CARBONS.— There are now 
several brands of cored projection carbons on the market 
designed particularly for use with alternating current. 
These carbons have a special chemicalization, and by reason 
of the gases produced not only give much steadier light than 
do ordinary carbons, but, also due to the chemicals, the light 
is of a whiter, more brilliant tone. Two of these brands 
have been thoroughly tried out and found excellent, viz.: 
The “Columbia White Flame A. C. Projector Carbons,” made 
by the National Carbon Company, and the “Alterno,” made 
by the Speer Carbon Company. These carbons are very 
much better than ordinary D. C. carbons for A. C. They 
should be used wherever an alternating current projection 
arc is operated. 

The Columbia white flame A. C. projector carbons were 
the first flickerless, noiseless and satisfactory alternating 
current combination ever used. These carbons reduced the 
noise of the A. C. projection arc to less than the usual shutter 
noise. The screen light was changed from a decidedly yel¬ 
low color to a snow white, with a remarkable increase in 
better seeing power, cleaner looking pictures, better per¬ 
spective, better film penetration, especially with tinted films, 
and brighter pictures. The candle power per arc watt (or 
per dollar spent for power) was improved from 10 to 30 
per cent. The latest results with these special A. C. carbons 
show a marked increase in screen candle power at high 
currents. This has opened a new era of development for 
A. C. arc projection with currents up to 100 amperes. 


WHAT DO YOU MEAN IT CAN’T 
BE DONE? 



390 


HANDBOOK OF PROJECTION FOR 


The Light Source 

W HERE the electric arc is the source of projection light, 
practically all illumination available for use comes 
from what is known as the “crater,” which is a more 
or less saucer-shaped depression formed on the tip of the 
positive carbon by the action of the current. When direct 
current (D. C.) is used at the arc there is only one crater 
formed, because a crater forms on the positive carbon only, 
and with D. C. one carbon is always positive and the other 
always negative. When alternating current (A. C.) is used 
at the arc, however, a different condition is set up, because 
a crater always forms on the tip of the positive carbon, and 
with A. C. at the arc each carbon is alternately positive and 
negative. It therefore follows that where A. C. is used at 
the arc a crater forms on the top of both the upper and 
lower carbon, and since the crater forming force of the 
current is thus divided, it also follows that the craters 
formed are very much smaller than those formed by an 
equal amperage of D. C. This is true to the extent that the 
combined area of the craters on both carbons of an A. C. 
arc will not equal the area of the single crater formed on the 
positive carbon tip of a D. C., arc amperage being equal* in 
both cases. 

USING A. C. ARC FOR PROJECTION.— Experience has 
amply demonstrated the fact that when using an A. C. arc 
for projection, best results are had when the light from one 
crater—the upper—is used. Any attempt to utilize the light 
from both craters will inevitably result in inferior results at 
the screen. True there are those who claim to have suc¬ 
cessfully used the light from both craters for projection, but 
we have yet to examine a single instance where the claim 
was made good when all the facts were examined. 

When we therefore consider that the light from only one 
crater is available; that the crater is very much smaller 
than the D. C. crater of equal amperage, and that the crater 
brilliancy per unit of area cannot be higher than that of the 
D. C. arc, it becomes manifest that the light available to the 
collector lens from an A. C. arc is very much less in amount 
than is the light from a D. C. arc of equal amperage, as- 


MANAGERS AND PROJECTIONISTS 


391 


suming the two arcs to be adjusted at the point of highest 
efficiency with relation to the collector lens. 

In this connection, however, let it be noted that for some 
reason never explained to our entire satisfaction, the light 
from an A. C. projection arc has a higher power of pene¬ 
tration and a whiter brilliancy than has light from the 
D. C. arc. 

While this may be accounted for in part by difference in 
chemicalization of A. C. and D. C. carbons, chemicalization 
cannot account for it all, as the same thing was to some 
extent true some years ago when the same carbons were 
used for both A. C. and D. C. We are inclined to believe 
it is in some measure due to the fact that the A. C. arc 
produces less gas than does the D. C. arc of equal amperage, 
and that the heavy D. C. arc stream operates to soften the 
tone of the light either by adding a yellow tinge or by 
screening out those rays which give the light the qualities 
named. This is, however, by no means made as a statement 
of fact. It is set forth merely as forming an interesting 
field for study by the projectionist, by carbon manufacturers 
and others interested. As a matter of fact the violet lines 
in the spectrum of the arc stream are said to be brighter 
than from the crater itself, this latter being tentatively ex¬ 
plained in two ways: (a) that the arc stream is higher in 
temperature even than the crater floor; (b) that the flow 
of current through the gas causes it, the gas, to have lumi¬ 
nosity without regard to its temperature, meaning that the 
current flow causes electro-luminescence, as in a vacuum 
tube or the aurora borealis. (See Professor Gage’s book on 
Optic Projection, Page 546.) 

CAUSE OF LIGHT. —The brilliancy or light producing 
power of the floor of the crater of an electric arc is due en¬ 
tirely to its high temperature. The reason the crater forms 
on the positive carbon is because it gets hotter than does 
the negative, and the reason it gets hotter is because it 
offers higher resistance. 

The various elements of the arc offer resistance in the 
proportions indicated by the following. Taking for ex¬ 
ample a 60 volt D. C. arc, we find the voltage drop caused 
by the various elements to be as follows: 

Positive crater causes a 35 volt drop. 

Negative carbon tip causes a 10 volt drop. 

Arc stream causes a 15 volt drop. 

This indicates to us that the positive crater offers 58 per 


392 


HANDBOOK OF PROJECTION FOR 


cent, of the total resistance of the arc, the negative crater 
only 17 per cent, and the gas stream 25 per cent. With this 
in view we readily see why the positve carbon tip gets very 
much the hotter of the two, why it burns away faster and 
thus forms a “crater,” and why it is very much the more 
brilliant of the two. 

CRATER TEMPERATURE.— The light giving power of 
the floor of the crater of an electric arc depends upon two 
factors, viz.: (a) its temperature per unit area, and (b) its 
total area. Its total light giving power will, therefore, be 
its candle power per unit area (usually taken in square 
millimeters) multiplied by its total number of units of area. 

So far as we know the actual temperature of an electric 
arc crater has never been accurately measured, but it has 
been estimated at 3.427 degrees Cent., or 6,200 degrees Fahr. 
(See Bulletin Bureau of Standards, Vol. 1, Page 909.). Later 
investigations, however, indicate that the temperature of 
the positive crater is decidedly higher than this. (See book 
by Lummer.) By comparison the temperature of the sun 
is given as about 6,500 degrees Cent., the acetylene flame 
2,057 Cent, and the ordinary gas flame 1,557 Cent. 

Whatever the exact measure of its heat in degrees, how¬ 
ever, it is that temperature necessary to volatilize carbon, 
the most refractory substance known to science, and it is 
this latter fact which makes it the most brilliant artificial 
light mankind has been able to produce. Much interesting 
and valuable information on the electric arc will be found 
in Optic Projection, Pages 536 to 571. 

CANDLE POWER OF CRATER. —Experiment has shown 
that under any given set of conditions the candle power of 
the crater of an electric arc, using cored carbons, remains 
stationary at somewhere between 130 and 160 c. p. per sq. mm. 
when the carbon is working at or near its capacity, but that 
this brilliancy per unit of area may be considerably lowered 
by working a carbon appreciably below maximum capacity. 

In other words, the brilliancy per unit of area is stationary, 
regardless of the number of amperes, provided the size of 
carbons in all cases be such that it will work at or near 
capacity. (See important foot note on page 412.) 

We may therefore say that, regardless of amperage, with 
a carbon working at or near capacity, its crater brilliancy 
will be about 150 C. P. per square mm., which figures out 48,- 
300 C. P. for a crater having an area of .5 of a square inch. 
Bearing this in mind it will be seen that increase in amper- 


MANAGERS AND PROJECTIONISTS 


393 


age will produce increase in total luminosity at the rate of 
about 150 C. P. for each square mm. increase in crater area. 

Experiments have determined that with a 55-degree crater 
angle, the crater area increase per ampere is a somewhat 
variable quantity with different makes of carbon. 

Note: At our request the National Carbon Company 
undertook experiments to determine, accurately, the effect 
of current increase on crater area. We are indebted to Mr. 
W. R. Mott, of the National Carbon Company laboratories, 
for the following remarkably complete and in every way 
excellent data : 


Data 

on Crater Area 

of Positive 

Cored Columbia 

Uppers 

with Columbia “Silvertip 

” Negative Lowers: 

TABLE NO. 18 


Size of 


Crater 

Crater 

Crater 

Carbon 


Area 

Width 

Length 

inch 

Amperage 

inch 

inch 

inch 

V2 

25 

.05 

.24 

.28 

Vs 

35 

.08 

.32 

.37 

H 

50 

.15 

.41 

.48 

Vs 

60 

.16 

.42 

.48 

Vs 

80 

.33 

.57 

.71 

Vs 

100 

.37 

.60 

.74 

1 mm. 

is .00155 of a square 

inch, or 645.2 

sq. mm. in 15 square 

inches. 


The area in the above cases was measured by means of a 
planimeter on the burnt form of the crater, which was ob¬ 
tained by impressing the white hot carbon on a block of 
hard wood. A further check on the area is obtained by 
using the formula for the area of an ellipse whose diameters 
are represented by the width and length of the crater as 
given in the above table. 

The direct observation of the length of the crater was also 
obtained by projecting an image of the arc with a magnifi¬ 
cation of 2.5. The average results of a number of tests of 
the length of the crater were as follows: 

TABLE NO. 19 


Size of 


Crater 

Positive Carbon 

Amperage 

Length 

Vs in. 

25 

.28 in. 

Vs in. 

35 

.34 in. 

Vs in. 

50 

.46 in. 

Vs in. 

60 

.48 in 

Vs in. 

80 

.67 in. 

Vs in. 

100 

.70 in. 


The results of the two methods give reasonable checks. 
As a result of much study of crater areas, we find it in¬ 
creases more rapidly than proportional to the current. 

If the current be doubled, the crater area increases 2.46 
times. The candle power of the carbon arc also increases 


394 


HANDBOOK OF PROJECTION FOR 


2.46 times when the current is doubled. In the form of the 
simplest mathematical terms this means that the crater area 
and candle power increase as the current to the 1.3 power. 
The following formula expresses this relationship: 

Crater area = KC 1 3 for crater area in square inches, in 
which C = current in amperes and K = .00092. K is cal¬ 
culated for Columbia carbons only. 

The error has been made by Messrs. Aryton, G. F. Binkel- 
man and others that crater area is proportional to the cur¬ 
rent. This is not true where the proper size of carbon for 
correct service is used for ordinary projection, or for search¬ 
lights. In the following table we have arranged together 
the observed and calculated results on the basis that crater 
area increases 2.46 times when the current is doubled. It 
will be noticed that the observed results and calculated re¬ 
sults agree satisfactorily. 


TABLE NO. 20 


Calculated 
Crater Area 
.06 sq. in. 
.15 sq. in. 
.37 sq. in. 


Observed 
Crater Area 
.05 sq. in. 
.15 sq. in. 
.37 sq. in. 


Amperage 

25 

50 

100 


HIGH AMPERAGE WASTEFUL.— It is thus seen that by 
increasing carbon size and amperage we may cause the 
generation of almost any number of candle power at the 
crater, but as will be shown, the projector lens system as 
now constituted, is unable to utilize the whole of the illumi¬ 
nation produced by a D. C. arc if current flow be in excess 
of about 60 amperes. Beyond that point there is unavoid¬ 
able loss, in increasing amount, as the current flow is in¬ 
creased until at about 120 amperes a point is reached where 
further increase in current flow brings no result in in¬ 
creased light at the screen. It is possible, though we be¬ 
lieve hardly probable, that improvements in the optical 
system may overcome this difficulty. 

The Speer Carbon Company has, at the request of the 
author, compiled the very complete data contained in table 
No. 21 as to crater area and arc voltage, at varying current 
strengths, for Speer Directo positives and Speer Hold-Ark 
negatives. 

The results appear in complete form in table No. 21, the 
results as to crater area found therein being summarized in 
Fig. 116. 

We feel that the thanks of the profession are due to the 
National Carbon Company and the Speer Carbon Company 
for having made such complete data available. 


MANAGERS AND PROJECTIONISTS . 395 

TABLE NO. 21 

Crater Areas of Projector Carbons at Different Amperages Direct Current 


■Speer Hold-Ark Negatives— N 



-Speer Directo Positives- 


Size of 

Crater 


Pos. 

Neg. 



Crater 

Area 

Angle 

Inch 

Inch 

Amps. 

Volts 

Inch 

Inch 

Degrees 

Vs 

7/16 

85 

56 

.603 x.784 

.3694 

56 



86 

O 1 

.600 x.788 . 

.3713 

55.5 



85 

55 

.537 x.739 

.3120 

56 



85 

58 

.538 x.750 

.3175 

56.5 



85 

0< 

.588 x.799 

.3689 

59 



85 

57 

.558 x.766 

.3357 

56.5 



86 

57 

.577 x.788 

.3562 

56.5 


Average 

85.4 

56.7 

.5715X.7734 

.3472 

56.5 





,—Speer Hold-Ark Negatives—, 


Speer Directo Positives- 


Size of 

Crater 


Pos. 

Neg. 



Crater 

Area 

Angle 

Inch 

Inch 

Amps. 

Volts 

Inch 

Inch 

Degrees 

% + 

Vs 

66 

52 

.455 x.628 

.2246 

56.5 



65 

53 

.440 x.631 

.2183 

00.0 



65 

52 

.464 x.629 

.2293 

59 



66 

53 

.467 x.657 

.2411 

59 



64 

51 

.447 x.619 

.2175 

54.5 



66 

52.3 

.483 x.640 

.2427 

58 


Average 

65.3 

52.5 

.462 x.6323 

.2273 

57.5 





( —Speer Hold-Ark Negatives—> 


Speer Directo Positives- 


Size of 

Crater 


Pos. 

Neg. 



Crater 

Area 

Angle 

Inch 

Inch 

Amps. 

Volts 

Inch 

Inch 

Degrees 

Vs + 

11/32 

45 

53 

.367 x.483 

.1392 

53.5 



46 

52 

.376 x.474 

.1321 

54 



46 

54 

.375 x.470 

.1385 

54 



45 

52 

.380 x.495 

.1477 

56 



46 

53 

.368 x.478 

.1381 

56 



45 

52 

.378 x.500 

.1483 

56 



46 

54 

.370 x.470 

.1365 

53 



46 

54 

.385 x.495 

.1467 

56.5 



45 

53 

.380 x.485 

.1447 

56.5 


Average 

45.5 

53 

.3754x.4832 

.14131 

55.0 





f —Speer Hold-Ark Negatives— v 


Speer Directo Positives- 


Size of 

Crater 


Pos. 

Neg. 



Crater 

Area 

Angle 

Inch 

Inch 

Amps. 

Volts 

Inch 

Inch 

Degrees 


5/16 

27 

45 

.287 x.354 

.0797 

54 



26 

45 

.291 x.341 

.0779 

54 



26 

45 

.273 x.353 

.0757 

53 



26 

46 

.275 x.359 

.0783 

55 



25 

45 

.278 x.355 

.0775 

54.5 



26 

47 

.265 x.352 

.0732 

53.5 


Average 

26 

45.5 

.277 x.3523 

.07705 

54 


WHAT HAPPENS WHEN AMPERAGE IS INCREASED. 

—The projectionist who has means available for increasing 
current flow gradually from about 25 to 100 amperes may 
conduct an experiment which should not only be interesting 
but highly instructive. He may even learn considerable if he 
can only increase amperage from about 25 to 60 or 80. Pro¬ 
ceed as follows: 

























396 


HANDBOOK OF PROJECTION FOR 


With 25 amperes D. C. flowing, and the crater carefully 
adjusted to give a good spot, place over the surface of the 
converging lens a metal plate in the center of which is a very 
small hole—the very smallest you are able to make. If 
necessary, have a jeweler drill the holes for you, using one 
of his smallest drills. Use very thin metal, such as thin tin, 
and do not place the metal in the slide carrier, but right up 
just as flat against the face of the lens as you can get it. 
Unless the plate actually rests against the glass at the point 
where the hole is, the experiment will not be satisfactory. 





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Figure 116. 


This will produce on the fire shutter of the projector a 
bright spot of light which may or may not be surrounded 
by a halo of considerable size. The small bright center is a 
pin-hole photograph of the crater of the arc. The result as 
to size of spot will depend upon relative distance of crater 
and aperture from optical center of the condenser, the 
enlargement of the crater image over the crater being as 
many times as the first distance is contained into the second. 

Having examined the spot of light thus produced, increase 
the current flow by 10 or 20 ampere steps, stopping on each 
change long enough for the crater to increase its area to 
conform to the increased amperage. You will find the image 




















































































































































MANAGERS AND PROJECTIONISTS 


397 


of the crater will increase in size with each increase in 
amperage, until finally it will cover the entire aperture. This 
latter point will be reached at somewhat varying amperage, 
depending upon the magnification of the light source at the 
spot. Ordinarily, however, we believe we are safe in saying 
that at between 50 and 60 amperes D. C. the image of the 
crater projected through the pin-hole in the center of the 
condenser will cover the entire aperture. 

When you have reached this point, pause and consider the 
matter. What does this mean? We shall presently see: 
When the point is reached where the crater image projected 
through the center hole covers the entire aperttire, substitute 
another plate in which is a similar hole drilled one-half an 
inch from the center of the metal plate—optical axis of the 
condenser. You will find that the image projected through 
this hole will not fall quite central with the aperture of the 
projector, but a little to one side. Also the crater image will 
not cover the entire aperture, though nearly so, amperage 
being equal to that required for the image projected through 
the center hole to just cover the aperture. By increasing the 
current flow a little beyond the amperage necessary for the 
image projected by the center hole to cover the aperture, you 
will find that the image projected by the hole a half inch off 
center will also cover the aperture. In other words, the 
latter crater image must be a trifle larger than the first one in 
order to cover the aperture, because its center is out of 
center with the aperture. 

Stop and think again. What does this mean? 

Next drill a third hole, of equal size with the others but 
one inch from the center of the plate. The image of the 
light source projected through this hole will have to be still 
larger than either of the others in order to cover the entire 
aperture, because its center is still further out of center with 
the aperture than was the last one. By increasing the 
amperage sufficiently, however, a point is reached where it 
is large enough to cover the entire aperture, but when that 
happens it is decidedly larger than the first central crater 
image and considerably larger than the second image. 

Again stop and think. What is the condition now? Why, 
just this: 

The condenser for a distance one inch in every direction 
from its optical axis is working at full capacity, insofar as 
has to do with an aperture of that size. In no possible way 
could any more light be gotten through an aperture of equal 


398 


HANDBOOK OF PROJECTION FOR 


dimensions under that condition as to magnification of light 
source at the aperture. The center zone of the condenser 
represented by a two-inch diameter circle is working at its 
absolute maximum capacity, insofar as has to do with an 
aperture of that size under that condition. 

By further increase in current flow the center zone can be 
made to pass an increased amount of light, yes, but it would 
all be wasted on the cooling plate, not a single ray getting 
through the aperture. 

If we now continue our experiment by drilling other similar 
size holes by half inch steps, clear out to the edge of the 
free diameter of the converging lens of the condenser, we 
shall find that increasing amperage produces less and less 
increase in light as more and more of the area of the con¬ 
denser comes up to its maximum working capacity, until 
finally, usually at about 120 amperes, it will be found impossi¬ 
ble to get more light through the aperture because the entire 
condenser is working to capacity. 

This explains why it is that when we increase the amperage 
up to say 55 amperes, the increase in light is about in propor¬ 
tion to the increased amperage, because up to that point none 
of the condenser is working up to capacity, but beyond that 
point it begins to slow up, and as more and more of the 
condenser comes up to maximum working capacity, the slow¬ 
ing up is more rapid, until a point is reached at about 120 
amperes where very little if any further perceptible screen 
brilliancy can be had. 

VALUABLE DATA.— The foregoing conclusion is support¬ 
ed in its entirety by experiments conducted by Mr. W. R. 
Mott, of the National Carbon Company’s laboratories, which 
were described in an article, “As to Increased Amperage and 
Screen Illumination,” Page 1186, May 24, 1919, issue of Moving 
Picture World, in which the experiments were described as 
follows: 

“The screen candle power was determined as the average of 
many readings with a Scharpe Miller Photometer Lamp 
standardized by the Bureau of Standards at Washington. The 
screen was a 7 by 9 foot with a 67 foot throw. The entire 
purpose was to obtain the percentage gain in candle power 
with increase in amperage, using proper size trims corres¬ 
ponding to the amperage. Columbia cored uppers were used 
with Columbia Silver Tip negative lowers. 

“Increase in current from 30 amperes to 50 amperes gave 
160 per cent, gain in screen candle power. 


MANAGERS AND PROJECTIONISTS 


399 


“Increase in current from 50 amperes to 70 amperes gave 
46 per cent, gain in screen candle power. 

“Increase in current from 70 to 90 amperes gave 18 per 
cent, gain in screen candle power. 

“Increase in current from 90 to 110 amperes gave 15 per 
cent, gain in screen candle power. 

“Increase in current from 110 to 130 amperes gave 12.5 per 
cent, gain in screen candle power. 

The above data were obtained with the usual lens system 
consisting of 6^4 and 7}4 inch focal length condensers, with 
a fourth size projection lens. 

“Beyond' 120 amperes D. C. the increased amperage gives 
no appreciable increase in screen brilliancy, nor is it possible 
with a projector aperture of the present size, to change this 
condition. 

ARC VOLTAGE. —A projection arc at a given amperage 
operates most efficiently with the carbon tips a certain given 
distance apart. Any alteration in this distance will operate 
to decrease the brilliancy of the light. This distance varies 
with the amperage, and what we call the “voltage of the 
arc” is the E. M. F. necessary to force the current from one 
carbon tip to the other against the comparatively high 
resistance of the arc stream. Put in another way, arc voltage 
is the electrical pressure or voltage necessary to force the 
current across the space between the carbon tips. The arc 
voltage is the reading of a voltmeter when it is attached to 
the upper and lower carbon arms, or carbons, with the arc 
in operation. Just what the actual best voltage value may be 
for different amperages we do not at this time know, nor do 
we believe that the matter could be set down in figures, 
because in our opinion much would depend upon the carbons 
themselves. The National Carbon Company, however, recom¬ 
mends Table 22 where their carbons are used, and data of 
value also appear in Table No. 21. 

It seems reasonable to suppose that, regardless of amperage, 
arc voltage would alter with volume and character of the arc 
stream, and there can be no doubt but that diffrent makes 
of carbon do give off gases which are not only of different 
volume but of different character. 

In this connection, we might add that there seems the possi¬ 
bility for development in projection carbon manufacture 
along this line. It may be possible that carbons could be 
developed which would, without any sacrifice in other direc¬ 
tions, provide a gas stream which would permit of, or even 


400 


HANDBOOK OF PROJECTION FOR 


demand, a comparatively wide separation of the carbon tips 
for best results, and this would act to automatically and 
entirely eliminate lower carbon tip interference, which now 
under many conditions operates to cut down the total illumi¬ 
nation delivered to the collector lens. 


ARC VOLTAGE WITH RELATION TO AMPERAGE FOR 
PROJECTION CARBONS 


Table No. 22 


Columbia Positives with 


Arc Amperage 
30 
40 
50 
60 
70 
80 
90 
100 


“Silver Tip” Negatives on direct 
current. 

Proper Arc Voltage 
52 
54 
56 
58 
60 
62 
64 
66 


For alternating current with Columbia White Flame 
Combination. 


Arc Amperage 
50 or 60 amps. 
70 
80 
90 


Arc Voltage 
28 
30 
32 
34 


INTERESTING DATA.— Simon Henry and Henry Phelps 
Gage, of Cornell University, have conducted experiments with 
D. C. regular carbon sets which resulted as follows : A 15 
ampere 50 volt arc taking current through a rheostat, con¬ 
suming 750 watts in the lamp and 1,650 watts in total, gave 
a total of 3,490 C. P., or 4.65 C. P. per watt of energy, con¬ 
sumed in the arc, or 2.12 C. P. per total watt consumed in the 
arc and rheostat. A 40 ampere 51 volt arc, taking current 
through a rheostat, consumed 2,040 watts in the arc, or 4,400 
watts total, and gave 12,350 C. P., which is 6.05 C. P. per watt 
consumed in the arc or 2.8 C. P. per watt consumed in both 
the arc and the resistance. 

An examination of these figures is interesting. It apparently 
shows a less C. P. per total watt of energy consumed in a 40 
ampere arc than in the arc of lower amperage, because while 
it is true there is a gain of 1.4 C. P. per watt of energy 
expended in the 40 ampere arc, as against the 15 ampere arc, 
there is an actual loss of .04 C. P. per watt when we come to 
examine the figures as applied to the total amount of energy 
expended. 

We are inclined to believe, however, that this slight loss is 


MANAGERS AND PROJECTIONISTS 


401 


chargeable to the fact that the voltage of the arc remained 
practically constant where in a projection arc there would 
be considerable variation as between a 15 and a 40 ampere 
arc. We do not quote these figures as having any consider¬ 
able value, except insofar as they point out to the projection¬ 
ist the possibilities for interesting experiments and study 
along these lines. 

In the course of these experiments it was shown that a 
mercury arc rectifier arc, using 40 amperes at 52 volts, regular 
D. C. carbon set, gave 12,150 C. P., a 40 ampere 27 volt A. C. 
arc gave 1,830 C. P., a 40 ampere 51 volt D. C. arc gave 
12,350 C. P., carbon set being the same in all cases, (see tables 
Pages 556-57 Optic Projection) which indicates that direct 
current through a rheostat and alternating, current taken 
through a mercury arc rectifier have approximately equal 
illuminating power, but when A. C. is used at the arc the 
illuminating power is very much less indeed. 

Through the courtesy of the Comstock Publishing Company 
we are enabled to present two charts illustrating the relation 



between the power consumption and candle power, in which 
it is shown that with the right angle lamp (Chart A) A. C. 
through a rheostat (resistance) gives the least amount of 
light per K. W., A. C. with a transformer gives more light 
than when a rheostat is used, and A. C. through a rectifier 
gives the greatest amount of light. D. C. with a rheostat 
gives less light per watt of energy consumed than does A. C. 














































































































402 


HANDBOOK OF PROJECTION FOR 


through a rectifier, while D. C., if only the power consumed 
at the arc be considered, gives the greatest illumination of 
all for a given power input, (left upper curve) i.e., 10,000 C. P. 
for less than 2 K. W. of power consumed. 

Chart B, in which the regular D. C. set is used, shows that 
A. C. with a rheostat (resistance) gives the least amount of 
light per K. W., D. C. with a rheostat next, A. C. with a 
transformer next, and A. C. with a rectifier the greatest 
illumination of all per watt of energy consumed, though the 
upper left-hand curve shows that straight D. C. gives the 
greatest amount of light of all if only the power consumed 
by the arc be considered, and the waste in rheostat be not 
taken into account. 

If the two diagrams be closely compared, it will be found 
that the right angle lamp gives the most light for the same 
current in every case, though the light given for the same 
power input is the same with both styles of lamps. With 
either A. C. or D. C. and resistance the right angle lamp gives 
the greater amount of light, but with A. C. and a transformer 
the right angle lamp gives the least light. This is due to the 
higher voltage of the right angle arc when used with A. C., 
the right angle arc requiring about 50 volts whereas the 
inclined carbon required but 30. 

In actual practice the foregoing conclusions must be modi¬ 
fied by the fact that D. C. through a rheostat is cheap in 
first cost of installation, also requires slight expense in 
upkeep of the apparatus thereafter, whereas the mercury arc 
rectifier is a rather costly piece of apparatus and there is the 
item of replacement of tubes, as well as other possible repairs 
to the machine to be taken into consideration, which we 
believe will fully balance if not more than balance the appar¬ 
ent gain of alternating current taken through a rectifier as 
against D. C. through a rheostat. It might also be mentioned 
that operation at higher amperage than is feasible with the 
mercury arc is frequently desirable. 

SETTING THE CARBONS. —In considering light for pro¬ 
jection, one item is of prime importance; viz: the position 
of the crater. This latter is a matter of literally huge im¬ 
portance and one to which projectionists have in the past 
paid altogether too little attention. Unlike the ordinary arc 
lamp, which directs its strongest light either downward, or 
both upward and downward, the primary purpose of the pro¬ 
jection arc is to direct its strongest light flux upon the face 
of the collector lens, and this purpose cannot be accomplished 


MANAGERS AND PROJECTIONISTS 


403 


i/ 

A 



unless the crater is in the 
best possible position, 
which means the position 
most nearly facing the 
collector lens. 

The position of the 
crater is to some extent 
influenced by the angle 
of the lamp as a whole, 
which same to some ex¬ 
tent will vary with the 
local conditions, because 
of the varying pitch in 
projection, but should be 
such that under ordinary 
conditions the carbons 
will have an angle of 55 
degrees with the floor of 
the lamphouse, or 35 
degrees with the face of 
the collector lens. 

By angle of lamp we 
mean the angle of the 
lamp with relation to the 
axis of the optical train. 
Most largely, however, 
and in fact we might say 
almost entirely, the posi¬ 
tion of the crater with 
relation to the lens is 
governed by the setting 
of the carbons with rela¬ 
tion to each other. In 
setting the carbons in 
the projector lamp and 
the adjustment of the 
carbon jaws of the lamp 
itself, it is of great im¬ 
portance that the carbons 
be absolutely in line with 
each other, and straight 
up and down as we would view them if we were to look 
through the condenser opening. In Fig. 118 we are presumed 
to be looking in through the condenser opening. A, Fig. 118, 


Figure 118. 


















404 


HANDBOOK OF PROJECTION FOR 


shows the upper and lower carbon not only in exact line at 
the tips of the carbons, but in exact line throughout their 
length. 



TESTING THE SIDE LINE. —Upon taking charge of the 
projection room one of the first duties of the projectionist 
should be to make sure the carbons of his lamps are in per¬ 
fect line side- 
wise throughout 
their entire 
length. This 
may be done by 
placing two new 
carbons of equal 
diameter in the 
lamp, and cen¬ 
tering their tips 
exactly with 
each other. Hav¬ 
ing done this he 
may, by remov¬ 
ing the conden¬ 
ser lenses and 
applying the 
straight edge to 
the sides of the 
two carbons and 
looking through 
the condenser 
opening, deter¬ 
mine whether 
the carbons line 
exactly through¬ 
out their length. 

At B we see a 
condition where 
the upper carbon 
is out of line 
with the lower, 
Figure 119. and at C we see 

a condition 

where both carbons are out of line sidewise. The result of either 
one of these conditions would be that while the arc might 
burn perfectly on a new trim, the crater would gradually 
move toward the side of the carbon tip as the carbons were 





MANAGERS AND PROJECTIONISTS 


405 


consumed, unless there be a constant sidewise adjustment of 
the carbons by the projectionist. 

This condition may be remedied by filing the carbon clamps, 
or with some lamps, by loosening the bolts which hold the 
carbon jaw to the carbon arm, whereupon it may be possible 
to slightly tilt the offending jaw. If it is necessary to file the 
jaws the job should be done very carefully, the lamp having 
first been removed from the lamp house and clamped in a 
vise so that the filing may be done without removing the 
carbon jaw from the lamp. 

Before making the test to determine condition B or C, Fig. 
118, be sure the carbons you use for testing are themselves 
perfectly straight throughout their length, since a 12-inch 
carbon with just a little bit of crookedness at the right place 
would throw the carbon out considerably at its tip. If the 
carbon shows a condition such as at B or C, it would be 
well, before finally deciding there is something wrong, to 
test the carbons themselves for straightness, or to substitute 
other carbons. The manufacturers are, however, operating 
within very close limits as to the straightness of carbons, and 
very few are faulty in this respect. 

Modern projection lamps have a side adjustment, so that 
when a new trim is placed in the lamp, the tips may be lined 
sidewise with each other by moving the carbon jaw. 

CRATER ANGLE. —The angle of the crater to the plane of 
the collector lens is controlled by the amount of advancement 
of the lower carbon tip ahead of the upper tip. What is 
meant by this is made clear in Fig. 119 in which the regular 
D. C. set is illustrated. If the two carbons be set central 
with each other a condition similar to that shown in diagram 
A, Fig. 120, will be set up, under which the strongest light 
from the positive crater will follow line X, which means it is 
thrown directly on the tip of the lower carbon. The angle 
of the crater shown in sketch A is 30 degrees from the optical 
axis. Under this condition the zone indicated by B, which 
includes the upper quarter of the collector lens, would receive 
little or no direct light from the crater, the zone between 
lines B and C would receive considerable light, and the lower 
part of the lens would be fairly well illuminated. Such a set 
would of course be impossible from the projection viewpoint. 

In sketch B, Fig. 120, we see a better condition, the crater 
being at an angle of 40 degrees to the optical axis. Under this 
condition the strongest light would follow broken line X. The 
whole surface of the collector lens would receive some direct 


406 


HANDBOOK OF PROJECTION FOR 


light from the 
crater but the 
illumination o f 
the upper half 
of the lens 
would be un¬ 
evenly illumi¬ 
nated. 

At C, Fig. 120-b, 
we see the ideal 
condition for a 
D. C. crater, the 
same being at 
an angle of 55 
degrees with the 
axis of projec¬ 
tion and an angle 
of 35 degrees 
with the face of 
the collector 
lens. Under this 
condition the 
strongest illumi¬ 
nation would go 
forward along 
the dotted lines, 
but the fact 
nevertheless re¬ 
mains that as 
between the 
lower and the 
upper half of the 
collector lens 
there would be 
no large differ¬ 
ence in illumina¬ 
tion. This latter 
is partly by rea¬ 
son of the fact 
that the crater 
is not flat, but to 
a considerable 
degree cup- 






V&J 


1 






o 



Figure 120A. 















MANAGERS AND PROJECTIONISTS 


407 



„ shaped, and 

n- 1 much of the 

light from the 
__ S lower half of its 

\y surface therefore 

is thrown in an 

w/ 

// 

y/L 

// 

-x-upward direc- 

tion - 

VD-, Sketch C 

\ \ ^ ^ shows the ideal 

\ condition, e x- 

\ cept that there 

\ is a slight inter- 

\ ference by the 

\pd lower carbon tip. 

\ At sketch D, 

\ Fig. 120b, we see 

\ the result of 

V advanring thp 


lower carbon tip 
too much. The 


-" effect is that a 

long skirt is 
0% S. formed on the 

X positive carbon, 

and the crater 


- siizZ _ ^ floor covers a 

* * very wide sur- 

f a c e. Another 
effect is that the 
X-J angle of the 

crater with rela¬ 
tion to the face 
of the collector 
lens is almost 
ideal, the same 
being an angle 
, of 80 degrees 


with the optical 
axis and 10 de- 

/ 

grees with the 
face of the col- 


Figure 120B. lector lens. 
















408 


HANDBOOK OF PROJECTION FOR 


This would be a splendid condition if it were practical, but 
it is not because, first, under such a condition it is impossible 
to maintain a steady arc; second, the skirt formed on the 
positive carbon is very likely to break off, leaving a very im¬ 
perfect crater, which of course would result in extremely poor 
illumination until a new one is formed; third, the floor of the 
crater is distributed over a very wide area, which is objec¬ 
tionable from two viewpoints, viz: (A), very large light source 
sets up serious difficulties with relation to the optical system; 
(B), the floor of the crater being distributed over such a 
wide area, its brilliancy per unit of area will not be up the 
maximum, due to the body of comparatively cool carbon 
lying so close to its face. 

MAINTAINING CRATER ANGLE.— It is an easy matter 
to maintain the crater at the angle of greatest efficiency (55 
degrees from the optical axis or at an angle of 35 degrees 
with the face of the collector lens) provided proper prepara¬ 
tion has been made for so doing. To maintain the crater 
at its angle of greatest efficiency, however, it is necessary 
that an image of it be projected, either to the wall, the floor 
or elsewhere, and the correct angle be laid off at the point 
where the image falls. 

The only objection to this procedure is that if the distance 
of the arc from the face of the collector lens be altered, as 
it may be, the position of the crater image will change. This 
objection is not, however, a serious one, becafise changes of 
the position of the arc will not occur frequently; in fact 
they will only occur when the focal length of the condenser 
is altered, or some other change is made in the optical 
system. Once the correct angle has been laid off on the 
wall, the floor or elsewhere, it becomes a very simple mat¬ 
ter to alter its position by laying out a new line, at the same 
angle, in the new crater image position. 

To project the crater image it is necessary to use either 
one of the appliances now on the market for this purpose, 
or to drill a very small hole in the lamphouse door exactly 
opposite the crater, and over this hole establish a lens. 
This lens may be a bit of broken condenser or even an old 
spectacle lens. The resultant image may be reflected to 
any desired point by placing a bit of mirror in front 
of the lens. 

As a matter of fact, projector manufacturers ought to, and 
at least one of them has, at our suggestion, incorporated in 
their lamphouse door a device for projecting the crater to 


MANAGERS AND PROJECTIONISTS 


409 


a small ground glass screen held out from the surface of 
the door perhaps \ l / 2 inches by means of a suitable frame. 
It would not be an expensive thing to do, and the angle of 
greatest efficiency could be laid out in the form of a series 
of scratch marks on the glass. By making perhaps three 
of these marks, about H of an inch apart, the crater image 
would always fall near one of them even though the distance 
from crater to lens be altered. The thing is practical and 
should be done. 

HOW TO FIND THE ANGLE.— In connection with the 
foregoing, the following directions may prove of value in 
enabling the projectionist to lay off a correct 55 degree 
angle for his crater image. 

Fig. 121 illustrates the crater angle and shows plainly ex¬ 
actly what the 55-degree angle really means, also it illustrates 
the fact that 


when the crater 
is at a 55-de¬ 
gree angle with 
the optical 
axis, it must be 
and is at a 35- 
degree angle 
with the face 
of the collector 
lens. This 
same thing is 
illustrated at 
C, Fig. 120B. 




/4? 

OPTICAL /F AXIS 



Figure 121. 


In Fig. 122 we have an illustration of how the inverted 
image of the crater will appear when projected through a 
pin hole in the lamphouse door. A shows the image as it 
will appear if projected through a pin hole in the door on 
the left-hand side of the lamphouse. B is the same when 
projected through a pin hole in the right-hand side of the 
lamphouse. When dealing with the image, the line repre¬ 
senting the optical axis should be drawn through point C, 
which is the tip of the crater image and represents the 
lower edge of the crater itself. 

It is not necessary to have a protractor in order to lay out 
a 55-degree angle. Open an ordinary two-foot carpenter’s 
rule, as shown in Fig. 123, until it is 5 1T / 3 2 inches between 
the two inside edges at the 8 and 18 inch mark when meas¬ 
ured straight across from one mark to the other. The 








410 


HANDBOOK OF PROJECTION FOR 


OPTICAL 

c 

c 

AXIS LINE 

L 





/ 



Figure 122. 
the 55-degree angle thereto. 


inside edges of the rule will then represent a 55-degree angle, 
so that if the upper edge of the lower side of the rule 
represents the optical axis, then the lower edge of the upper 
side of the rule will represent the correct crater angle. 

It is not even necessary to use a rule. Just make a dot on 
a sheet of white paper and draw a straight horizontal line 
from it 6 inches long, then draw another straight line 6 
inches long, one end of which will meet the other line at 

the dot and the 
other end be 
5 17 /32 inches 
from the outer 
end of the first 
line, measuring 
straight across 
from line end 
to line end. 
The first line 
represents the 
optical axis 
and the other 
The two lines are exactly the 
same thing as the inside edges of the rule. 

Fig. 124 illustrates another method of laying out the 55- 
degree angle. Secure a sheet of cardboard about 6 by 8 
inches in size. Trim side A-B with a straight edge. Draw 
lines C-D at right angles to side A-B and then lay out line 
F-E at a 55-degree angle to line C-D. Having done this, 
strike an arc and when the crater is thoroughly well burned 
in and the light properly adjusted at the spot, pull the pro¬ 
jector table switch and allow the carbons to cool. Open 
both lamphouse doors and place the cardboard inside the 
lamphouse, with side A-B resting against the front wall of 
the lamphouse, or the condenser mount, and against the side 
of the carbons. Make a line on the cardboard by drawing 
a pencil across the face of the crater. If this line is parallel 
with line F-E, all is well; if not, then readjust the carbons 
and burn the crater until you get it right, or so that the 
two lines will have the same angle. When this point in the 
proceedings, is reached, project a crater image and mark 
the angle on the floor, wall or wherever the image falls. 

This latter method is not a very accurate one, but it will, 
nevertheless, serve fairly well if the various steps be taken 
with care, particularly in the matter of marking the angle 
of the crater. 



MANAGERS AND PROJECTIONISTS 


411 


Still another method, and one which combines the ad¬ 
vantage of a fair degree of accuracy with ease of application 
under all conditions, is as follows: Assuming that no means 
already exists for projecting the arc crater, drill a very 
small hole through the lamphouse door exactly opposite the 
edge of the floor of the crater. An inverted image of the 
crater will, of course, be projected through this- hole. Just 
at the lower edge of the pin hole draw a line on the lamp- 
house door representing the optical axis of the lens system. 

Now with a bit of looking glass reflect the image of the 
crater back to the hole in the lamphouse door and note its 



position. Next draw an angle line at 55 degrees with the 
optical axis line and then adjust the carbons until the crater 
is burned so that its reflected image matches this line, 
whereupon pull the switch. You now have your crater 
burned at a 55-degree angle and may mount in front of the 
hole a suitable lens and bit of mirror set to reflect the 
image to any desired point on the ceiling, floor or elsewhere. 
Having done this, strike the arc again, and before the crater 
has any time to change its angle, draw a line along the 
edge of the reflected image of the crater, wherever it may 




412 


HANDBOOK OF PROJECTION FOR 


be. This line will represent the 55-degree angle of the 
crater, and by holding the crater image to the line you will 
have it burning efficiently. 

Of course if your lamphouse already has some means of 



projecting the crater image, it will act to modify the fore¬ 
going instructions. If there is a big hole covered with 
colored glass, it will be necessary to remove the glass, cover 
the hole with metal and then proceed as per the instruction^. 

Note. —Since Blondel’s experiments great improvements have 
been made in carbons, so that the c. p. per sq. mm. of projection 
carbon arcs is now nearer 160 than 130. We have therefore 
arbitrarily selected 150 as an approximation (rather under than 
over ) of the sq. mm. candle power of projection carbon arcs .— 
Author. 




MANAGERS AND PROJECTIONISTS 


413 


Resistance as Applied to the 
Projection Circuit 



HERE is no difference in principle in resistance as ap¬ 


plied to the projection circuit and in resistance as ap- 


plied to any other circuit, but in practical application 
the differences are such that a somewhat extended explana¬ 
tion of resistance as applied to the projection circuit is 
necessary, particularly in view of the fact that the element 
of variable resistance enters very largely into the matter. 

The projection circuit is supplied by a voltage which is 
presumed to be a fixed quantity. This may be anything 
from 50 to 500 volts, though ordinarily it is either 60, 70, 
110 or 220. On the other hand the amperage necessary to 
projection under different conditions is an extremely variable 
quantity. In stereopticon projection it may be as low as 
12 amperes. For the projection of motion pictures anything 
from 25 to 120 amperes may be required, 25 representing the 
minimum arc projection for theatrical work, and 120 the 
maximum amperage from which any gain in light may be 
had through the projection optical system as at present 
constituted. With a given supply voltage, 110 for example, 
taken from a power distribution system the resultant 
amperage at the arc will depend entirely upon the amount 
of resistance opposed to the current flow. 

Before attempting to study resistance as applied to the 
projection circuit the student should gain a comprehensive 



B 



C 


Figure 130. 















414 


HANDBOOK OF PROJECTION FOR 


understanding of the operation of resistance as applied to 
all electric circuits, which may be had from a study of the 
matter under the general heading “Resistance,” Page 60. 

When resistance is spoken of in connection with a pro¬ 
jection circuit, what is meant is rheostatic resistance, or the 
resistance of the “rheostat,” which consists either of a series 
of wire coils composed of high resistance wire (see “Prop¬ 
erties of Resistance Metals,” Page 67), or a series of cast 
iron grids, which are in effect wires made of cast iron. 
These coils or grids are mounted in a frame, .from which 
they are completely insulated; they are also protected by a 
metal casing or covering, and in the case of the adjustable 
rheostat there is a dial switch by means of which a portion 
of the resistance may be either eliminated or put into use, 
at the will of the man in charge, as will be described. 

In Fig. 130, at A, we see the diagrammatic representation 
of an arc lamp connected directly to the supply wires, 
without any rheostatic resistance interposed. Under this 
condition it will be readily understood that the instant the 
carbons are brought into contact a dead short circuit will 
be formed, which will blow a fuse. At B, Fig. 130, we see 
a similar lamp connected to the same supply wires, but with 
rheostatic resistance C connected in series with the arc. 
This resistance operates precisely the same as does any 
other resistance, such as, for instance, that of the filament 
of an incandescent lamp. Disregarding technicalities, the 
rheostat opposes sufficient resistance to allow the passage 
of a certain predetermined number of amperes, the number 
of amperes passing being dependent upon the supply voltage 
and the number of ohms resistance in the rheostat. 

A.s. has already been explained, however, on Page 56, 
this is only true so long as the carbons remain in contact 
with each other. With the carbons in contact the number 
of amperes flowing would be equal, roughly, to the supply 
voltage divided by the number of ohms resistance in the 
rheostat. The instant the carbons are separated, however, 
and an arc is struck, additional resistance is established in 
the arc itself, the amount of which will vary with the 
number of amperes flowing, see Page 400, so that the 
actual current flow will be equal to the applied voltage 
divided by the sum of the number of ohms resistance con¬ 
tained in the rheostat and the arc lamp circuit; this latter 
being, for practical purposes, disregarded. 


MANAGERS AND PROJECTIONISTS 


415 


The resistance of a projection arc is to all intents and 
purposes a fixed quantity for any given number of amperes, 
because the projection arc operates at its point of highest 
efficiency, both in the item , of current consumption and in 
the item of light delivered, with a certain fixed separation 
of the carbons for each different current strength. 

As has been remarked, the supply voltage of each theatre 
is presumed to be, and should be a fixed quantity. By this 
we mean the theatre is supplied with current the voltage of 
which is presumed to remain constant at a certain given 
pressure, say 110 volts. The projection arcs at one theatre 
may require 45 amperes D. C. and at another theatre 60 
amperes D. C. How may this requirement be met, when 
both theatres have 110 volt current supply? 

The answer is simple. The change in amperage is ac¬ 
complished by varying the amount of resistance in rheostat 
C, diagram B, Fig. 130. This resistance may be made of 
sufficient amount to reduce the amperage to almost any de¬ 
sired quantity, or it may be slight enough to allow the 
passage of any number of amperes within the capacity of 
the wires and apparatus. 

VARIABLE AND FIXED RESISTANCE. —There are two 
types of rheostat, namely, the “fixed resistance” and the 



“variable resistance.” A fixed resistance rheostat is one 
in which no means is provided by the use of which the re¬ 
sistance it offers may be varied at the will of the man in 
charge. It consists of a number of coils of resistance wire, 
or a number of cast iron grids mounted in the usual way, 
with a binding post at either end of the resistance element, 
so that the current must pass through the entire resistance. 























416 


HANDBOOK OF PROJECTION FOR 


It is, however, not only possible, but the common practice 
to so construct rheostats that the amount of resistance sup¬ 
plied may be varied at will, merely by moving the lever of 
a dial switch attached to the rheostat, which, of course, has 
the effect of altering the number of amperes at the arc. 
Such an instrument is what is known as an adjustable 
rheostat. The principle of its operation is illustrated in 
Fig. 131, in which A-B are the supply lines, the rheostat in 
this instance being connected into line B, which is the 
positive. Line B connects to lever 6, which is the arm or 
the lever of dial switch; 1, 2, 3, 4 and 5 being its various 
contacts. 

An examination of this diagram will show that with the 



Figure 132. 


lever on contact 5 the current must pass through the entire 
eight coils of the rheostat, hence with the lever in this 
position the rheostat is oppoing its maximum resistance to 
the supply voltage, therefore reducing the amperage to a 
minimum. Should we however move the lever to contact 4, 
it will be readily understood that the current will pass 
down wire 4, entering the resistance at the bottom of coil B, 
which has the effect of eliminating coil A and reducing the 
total resistance of the rheostat by whatever amount of re¬ 
sistance coil A supplies. 

If lever 6 be on contact 3, then the resistance of both 
coils A and B will be eliminated. If the lever be on contact 
2 then the resistance of coils A, B and C will be eliminated, 
and if the lever be on contact 1 then the resistance of 




























MANAGERS AND PROJECTIONISTS 


417 


coils A, B, C and D will be cut out, and we will only have 
remaining the resistance of coils E, F, G and H. The re¬ 
sistance of these last four coils is what is known as the 
“fixed resistance” of an adjustable rheostat. It is the 
amount of resistance which cannot be cut out by means of 
the adjusting switch. It must be sufficient to withstand the 
pressure of the supply voltage without overheating. In other 
words : the fixed resistance of an adjustable rheostat must 
offer sufficient resistance to prevent enough current passing to 
overload the wires or grids composing the fixed resistance. 

In Fig. 132 we see the photographic representation of a 
rheostat coil and a rheostat grid. It will be observed that 
the grid is really the equivalent of the wire coil, except 
that it is made of cast iron. 

There are several different kinds of rheostats, but the 
adjustable rheostat is the one now most largely used in 
projection work. Another type of rheostat which is semi- 
adjustable is made up of several separate fixed resistance 
cells or rheostats mounted in a single case, so that the 
amount of resistance delivered by the whole may be altered 
by changing the connections to include a greater or less 
number of the total number of cells. These rheostats were 
considerably used in the earlier days of projection, but have, 
for the most part, been discarded in favor of the more 
convenient adjustable rheostat. 

HEATING. —A rheostat will continue to perform its office 
even though its coils or grids are red hot, but if worked 
under these conditions the life of the coils or grids will be 
very greatly shortened. Also when thus overloaded the 
temperature of the coils or grids may at any time reach a 
degree sufficient to fuse the metal, thus stopping all cur¬ 
rent flow and necessitating a somewhat difficult repair. 

Rheostats should never be worked at high temperature. 
The heat in rheostat coils or grids should under no cir¬ 
cumstances exceed 900 degrees F. 

Of course the projectionist will not be in position to 
measure such high temperatures, but a temperature of 900 
degrees is one which will cause the rheostat coils to become 
visible in a dark room. A dull red heat is approximately 
1,300 degrees Fahrenheit, while a cherry red is 1,500 degrees. 
If you use your rheostat at such high temperatures as wil/ 
make the coils show red in daylight it will not last long. 
As a matter of fact even the 900 degree temperature is too 


418 


HANDBOOK OF PROJECTION FOR 


high for true economy. Five hundred degrees Fahrenheit is, 
everything considered, as high as your rheostat ought to 
operate, and if it is not allowed to exceed this temperature 
the life of the coils and grids will be very greatly prolonged. 

In practice this means that if the coils are not allowed to 
reach a temperature which will make them visible in a dark 
room the rheostat will last many times longer than it will 
if the coils are operated at a temperature which will render 
them visible. The projectionist thus has a very good and 
practical check on rheostat capacity. If it is delivering 
satisfactory amperage and its coils cannot be seen in a 
dark room all is well. If when it is delivering the desired 
amperage it is found that the coils are visible in a dark¬ 
room, then it will be true economy to cut down the amper¬ 
age, if it is an adjustable rheostat, and add a second rheostat 
in multiple in order to get the desired current flow. If it is 
a fixed resistance rheostat it has not sufficient resistance, 
and resistance should be added as per Fig. 133. 

As a matter of fact if exhibitors would install two 
rheostats working at less than capacity, instead of one 
working at full capacity, the general results would be very 
much better, and the two rheostats would last ten times as 
long as the single rheostat will when working at capacity. 

RHEOSTAT REPAIR.— It is an excellent plan to have on 
hand a few extra rheostat coils or grids, so that repairs may 
be made by the projectionist in case a coil or grid burns in 
two or is broken. Making such repairs is, or should be, 
entirely within his capacity. The installation of a coil or 
grid requires only a little knowledge and careful work. The 
method of locating a grounded coil or a fault in the insu¬ 
lation is described on Page 1 358. The method of removing 
the grid or coil from the rheostat and replacing it with a 
new one will, of course, vary with different kinds of rheo¬ 
stats, but the principle is always the same. 

The main thing to remember is that all coils or grids must 
be completely insulated from the supporting frame, and 
alternate ends of the coils or grids must be insulated from 
each other. 

Remember that, no matter what the form of your rheo¬ 
stat may be, whether round, rectangular or square, whether 
of fixed or variable resistance, or whether of coils or iron 
grids, its electrical action is always precisely the same. The 
current enters at one end of a series of coils or grids and 
must pass through the entire length of each coil or grid 


MANAGERS AND PROJECTIONISTS 


419 


consuming a portion of the voltage in the process of over¬ 
coming the resistance. 

One point which is apt to puzzle the novice is that the 
voltage of the arc varies comparatively little, and if it be 
true that the voltage is reduced according to the amount of 
resistance in the rheostat, why is not the arc voltage varied 
more greatly when a portion of the rheostatic resistance is 
cut in or cut out? 

The answer is simple. The resistance of the arc and the 
resistance of the rheostat are two entirely separate ele¬ 
ments, and the resistance of the arc is dependent entirely 
upon the separation of the carbons and the kind and 
character of the arc stream. These elements are not in any 
way connected with the item of rheostatic resistance. No 
matter what the resistance of the rheostat may be, the 
resistance of the arc will be such as is set up by the con¬ 
ditions prevailing at the arc, which are dependent upon 
the elements just named. 

INSULATE YOUR RHEOSTATS.— The rheostat as a 
whole should always be thoroughly insulated from ground. 
This may best be accomplished by placing the rheostat on 
a slate or marble shelf, but it may also be done by setting 
it on sheet asbestos, asbestos millboard or some other heat 
resisting insulating material. 

Unless the rheostat be thus insulated from ground it is 
always possible that one of the coils may sag against the 
outer casing, or through some fault in the insulation be¬ 
come grounded to the frame of the rheostat, in which event 
if the rheostat as a whole be grounded there is likely to be 
current leakage. Such leakage may be sufficient to be im¬ 
mediately detected, but if the ground is one offering high 
resistance it is entirely possible the leakage may continue 
for an indefinite time without being discovered and every 
bit of current thus wasted will be registered on the meter. 
Should one of the coils sag against the casing, or should the 
coils become in any way grounded to the frame, and the 
support of the rheostat offer a path of comparatively low 
resistance to a wire of opposite polarity it is likely a fuse 
would blow. 

All trouble of this kind is avoided by placing the rheostats 
on insulating material. 

In the past is has been no uncommon thing to have a 
theatre manager complain of excessive current bills, only 
to find, upon investigation, the loss to be entirely due to 


420 


HANDBOOK OF PROJECTION FOR 


leakage from the rheostats. In such cases the ground was- 
of such high resistance that the leakage was not sufficient 
to either overheat the wires or blow the fuses, but it was of 
considerable amount, and the leakage was constant every 
moment the rheostat was in use. 

WARNING.—Rheostats should never, under any condi¬ 
tions, be placed on an iron covered shelf, or on any other 
material connected with ground which will carry current in 
event of the resistance element becoming grounded to the 
frame of the rheostat. Always place rheostats ON NON- 
INFLAMMABLE INSULATING MATERIAL. 

COOLING THE RHEOSTAT.— One excellent way of dis¬ 
sipating the heat generated by the rheostat and blowing it 
out of the room is to set the rheostat in front of an opening, 
in some location where it will be safe to remove the outer 
casing. Remove the outer casing and set a small fan in front 
of the coils or grids in such way that the blast from the fan 
will blow through them and blow the heat out of the room. 
This has the double advantage of getting rid of the ob¬ 
jectionable heat and increasing the capacity of the rheostat. 
(Also see “New Rheostat,” Page 437.) 

LOCATION OF RHEOSTATS.—Rheostats become hot— 
sometimes very hot. It is therefore unsafe to locate them 
very close to any sort of inflammable material. Rheo¬ 
stats should never be located within less than one foot of 
any wall containing inflammable material unless a sheet 
of inch asbestos be established between the rheostat and 
the wall, with at least a two inch air space between the 
asbestos and the wall. Rheostats should, of course, be 
thoroughly protected against any possible contact with 
inflammable substance of any kind. 

As regards the location of rheostats in the individual pro¬ 
jection room, so very much depends on the local condition 
that only general rules can be given, (a) Where it is prac¬ 
tical it is always best to locate the rheostats outside the 
projection room. This is particularly true in warm climates. 
The projection room is likely to be more or less uncom¬ 
fortably warm in summer, and if we add to the heat gene¬ 
rated by the electric arcs and the natural heat of the 
weather the heat of anywhere from one to three rheostats, 
a very uncomfortable condition is likely to result. It is 
quite entirely possible to place an adjustable rheostat out¬ 
side the projection room and so connect the lever of its dial 
switch by means of a series of levers and rods, or cords, as 


MANAGERS AND PROJECTIONISTS 


421 


to enable the projectionist to alter the position of the dial 
switch at will from working position beside either pro¬ 
jector. 

If conditions make it necessary to locate the rheostats in¬ 
side the projection room then they should preferably be 
located near the ceiling, and if possible under a vent leading 
directly to the open air. 

If it is not practical to have such a vent from the rheostats 
to the open air, then a hood should be provided, with a pipe 
leading therefrom directly into the projection room vent 
flue, so that the heat generated by the rheostats will be 
carried away. 

Under no circumstances should rheostats be located on or 
near the floor of a projection room. Such location will not 
only breed discomfort in warm weather but will be de¬ 
cidedly dangerous, because of possible contact with film or 
other inflammable material. 

EXAMINING CONNECTIONS.— It is important that the 
binding posts of the rheostat be frequently and carefully 
examined. Metal oxidizes under the action of heat, and if 
the rheostat terminals be left too long without attention, a 
thin scale is apt to form between the wire or the lug and 
the metal of the binding post. This scale may be quite 
visible, or it may be practically invisible. In either event it 
offers very high resistance. 

It is an excellent plan to loosen the terminal connections 
of the rheostat at stated intervals (the length of same to be 
dependent upon the number of hours per day they are in 
use) and clean them thoroughly, either by the use of sand¬ 
paper, emery cloth or by scraping. This is particularly 
important if the rheostat be working at or above capacity. 
Where rheostats are used several hours every day, once a 
week is none too often to do this. 

ADDING EXTRA RESISTANCE.— Should your rheostat 
deliver too much current when all the resistance is “in,” or 
if from any other cause you should desire to increase its 
resistance, you may do so by mounting one or more extra 
rheostat coils as per A, Fig. 133. It is also possible to in¬ 
troduce extra resistance in this way by making up some 
coils of No. 8 soft iron wire (or larger size if it be a rheostat 
of larger amperage capacity), though this is not recom¬ 
mended, since iron wire has a very high temperature 
coefficient. 

The extra coils may be mounted on porcelain insulators, 


422 


HANDBOOK OF PROJECTION FOR 


such as are used for mounting electric circuit wires. The 
ordinary porcelain knob insulators will do. These extra 
coils may be mounted on a brick wall or on a suitable iron 
frame, but they must not be placed near anything in¬ 
flammable ; they must also be protected by an outer casing 
the same as the regular rheostat coils. Wire screening hav¬ 
ing about 54 inch mesh is suitable for protection. These 
coils may either be mounted near the rheostat, or at some 
distance from it, connection being made between them and 
the rheostat by means of a suitable size copper wire. 

IRON WIRE RHEOSTATS. —It is possible to construct a 
rheostat from ordinary iron wire, but such wire has a very 
high temperature coefficient, which means that its resistance 



increases rapidly with the increase of temperature. The 
result of this is that if you build an iron wire rheostat 
capable of delivering the amperage you want after it be¬ 
comes hot, it will give altogether too much when you first 
strike the arc. 

OBJECTION TO BIG GRID RHEOSTATS. —As has been 
said, the temperature coefficient of cast iron is high. This 
means that a cast iron conductor of given area will deliver 
very much more current when it is cold than when it is hot. 
This forms one of the objectionable features of the cast 
grid rheostat, but the objection is not serious when rheo¬ 
stats of small size are considered. ^Vhen we come to con¬ 
sider the cast grid rheostat of large size, however, it 











MANAGERS AND PROJECTIONISTS 


423 


presents a different aspect, because if it is made to give a 
certain given current flow when heated to working tem¬ 
perature there will be a tremendous rush of current when 
the arc is first struck and the grids are cold. Big cast iron 
rheostats should therefore have some means provided for 
cutting in extra resistance until the grids heat up. 

The grid rheostat presents certain advantages, also cer¬ 
tain disadvantages as set forth below: 

Advantages. Disadvantages. 

(a) Better able to withstand (a) It is more difficult to re- 


high temperatures with¬ 
out damage. 

(b) Grids are less likely to 
sag and become grounded 
to the casing than coils. 

(c) Grids give longer serv¬ 
ice than coils. 

(d) They deteriorate very 
slowly. 


place broken grids than 
to replace coils. 

(b) The grid rheostat is 
much heavier than the 
coil rheostat of equal 
capacity. 

(c) Grids can be broken by a 
heavy jar. 

(d) Temperature coefficient 
low and less fixed, there¬ 
fore the grid resistance 
is somewhat less reliable. 


TEMPORARY REPAIR. —Should a coil or grid burn out it 
is quite possible to make a temporary repair as per Fig. 133, 
in which B is an asbestos covered No. 6 copper wire doubled, 
and C the broken coil. It is not necessary to describe the 
operation, because the illustration shows clearly how it is 
done. The reason for doubling the No. 6 copper is that it 
will be subjected to high temperature. Such a repair elim¬ 
inates a single coil, but almost any rheostat used for pro¬ 
jection purposes may be used temporarily with one of its 
coils cut out. It is, of course, understood that such a repair 
is only intended for strictly temporary use. 

RHEOSTATS CONNECTIONS.— Rheostats may be con¬ 
nected into a projection circuit either singly, “in series” or 
“in multiple.” The various series and multiple connections are 
perhaps one of the most puzzling things the novice has to 
contend with; also a large percentage of the “operators,” and 
even some projectionists do not understand the matter any 
too well, yet it is quite simple. 

Fig. 134 is the diagrammatic representation o‘f what is 
known as the series connection. In this connection we find 
two 2-ohm rheostats connected in such way that the re¬ 
sistance of both is opposed to the voltage as a single element. 


424 


HANDBOOK OF PROJECTION FOR 


In other words, instead of 2-ohms resistance opposed to the 
voltage, as would be the case if we had but a single rheostat, 
4-ohms resistance is opposed. Disregarding the resistance of 
the arc, if the supply current were 110 volts and we had but 
a single 2-ohm resistance rheostat connected in there would 
be a resultant current flow of 110 -s- 2 = 55 amperes. 



Figure 134. 


If we now connect another 2-ohm rheostat in series as 
per Fig. 134, we will have 4 ohms opposed to the current, 
and, again disregarding the arc resistance, we would as a 
result have 110 4 = 27.5+ amperes current flow. Please 

understand clearly that this would not be the result of the 
connection shown in Fig. 134, because in addition to the 4 
ohms opposed by the rheostats there would be the resistance 
of the arc added thereto. In the above we are merely 
showing you the way the thing operates—not working out 
accurate results. The actual total resistance of such a com¬ 
bination, including the arc, would be about 5 ohms, hence 
the actual current flow 110 h- 5 = 22 amperes. 

MULTIPLE CONNECTION. —The multiple connection is 
one which puzzles many, yet it is a very simple matter, once 
one gets a clear idea of the principles involved. 

Fig. 135 is the diagrammatic representation of a water 
main, A, connected to the supply pipe B of a motor by 
means of two small pipes in which valves C-D are installed. 



Figure 135. 












MANAGERS AND PROJECTIONISTS 


425 


The pressure in pipe A we will assume to be 110 pounds. 
If we open valve C, its full capacity will flow from pipe A 
into pipe B, and be used by the motor. Under this con¬ 
dition that is all the water the pressure in pipe A will be 
able to force through pipe C into pipe B. If pipe C were 
the only connection between pipes A and B, then the 
capacity of pipe C would be all the water which could pos¬ 
sibly reach the motor. 

In addition to pipe C, there is, however, pipe D. We open 
its valve and instantly the amount of water flowing into 
pipe B is doubled ; also the power of the motor is doubled. 

Precisely what water does in Fig. 135 the electric current 
does in a multiple rheostat connection. 



In Fig. 136 we have precisely the same thing as applied to 
electrics. A and B are the wires of a projection circuit, C-D 
two rheostats and E-F two single pole knife switches. It 
requires no large understanding to see that if we close switch 
E the arc will receive amperage equally to the capacity of 
rheostat C. If we then close switch F the arc will in addition 
receive the capacity of rheostat D. This is what is known as 
a “multiple connection,” which is again diagrammatically rep¬ 
resented in Fig. 137, in which the connection is shown in two 
ways, the 25 ampere dotted line in A representing the resist¬ 
ance of the coils or grids. If you will carefully trace out the 
connections in diagrams A and B Fig. 137 you will find they 
represent precisely the same thing as the water pipe connec¬ 
tion in Fig. 135 and the connection shown in Fig. 136. 

Any number of rheostats of different type or different volt¬ 
age may be connected in series, provided the total resistance 
of the whole be sufficient to reduce the current flow to a 
point where neither wires or resistance will be overloaded. 

Any number of rheostats may be connected in multiple. 









426 


HANDBOOK OF PROJECTION FOR 


provided each individual rheostat has sufficient resistance to 
oppose the line voltage without overload, and further provided 
that the resultant amperage be not great enough to overload 
the circuit wires, arc lamp or apparatus. For instance, a 10 
ampere, a 50 ampere and a 25 ampere 110 volt rheostat may be 
connected in multiple on 110 volts. The result would be a 
current flow equal to the combined amperage capacity of the 
rheostats, or 10+50+25=85 amperes, hence the circuit wires 
etc. must have at least 85 amperes capacity. 

You may use a 220 volt rheostat on 110 volts, or on any 
other voltage not in excess of 220. You would not, however, 




Figure 137. 


get amperage equal to the rated capacity of the rheostat 
except on 220 volts. You cannot, however, connect 110 volt 
rheostats either singly or in multiple on 220 volts, because they 
have not sufficient resistance to withstand that pressure. If 
110 volt rheostats were connected either singly or in multiple 
on 220 volts the coils or grids would get white hot and burn 
out very quickly. You may, however, connect two 110 volt 
rheostats in series on 220 volts, by reason of the fact that you 
would in effect be making one rheostat out of the two, thus 
presenting double the resistance required for 110 volts. Two 
110 volt rheostats connected in series would, however, be 
























427 


MANAGERS AND PROJECTIONISTS 

slightly overloaded (we speak of rheostats made for use 
on a projection circuit) because of the fact that such rheostats 
are made to operate in conjunction with an arc, the resistance 
of which is figured in the total, so that if the arc produced 
one ohm resistance and the rheostat two ohms, then the total 
would be three ohms when connected singly, but when con¬ 
nected in series instead of having six ohms there would only 
be five, because the resistance of one arc would be absent. 

You may use a rheostat built for a certain voltage on that 
voltage or on anything less than that voltage, but you cannot 
use a rheostat on a higher voltage than it is built to with¬ 
stand, unless it be placed in series with additional resistance; 
though this latter is qualified to the extent that a rheostat 
built for a certain voltage may usually be used on current 5, 
10 or even 15 volts in excess of that pressure. 

A. C. and D. C. RHEOSTATS. —The novice often asks: 
What is the difference between an A. C. and a D. C. rheostat? 

There is no such thing as an A. C. or D. C. rheostat. Any 
rheostat will work either on A. C. or D. C., but a rheostat 
which will deliver 30 amperes to a projection arc when con¬ 
nected to 110 volt D. C. supply wires, will deliver a somewhat 
higher amperage on the same voltage A. C. This is because of 
the fact that an A. C. projection arc is shorter, hence offers 
less resistance than the D. C. projection arc of equal amper¬ 
age, therefore the total resistance opposed to the current by 
the rheostat and the arc is reduced. 

This is, however, qualified by the fact that there is some 
tendency to inductive effect when a wire coil rheostat is 
used on A. C., which has the effect of adding inductive resist¬ 
ance, or in other words “magnetic kick” to the ordinary 
resistance offered. The amount of inductive restisance thus 
set up will vary with the size of the coils, their length and the 
spacing of the spirals. It amounts to something, though not 
very much. The inductive effect, however, does cause vibra¬ 
tion in the coils, with the result that some wire coil rheostats 
are very noisy when used on A. C. This noise may be reduced 
by packing the center of the coils tightly with threaded as¬ 
bestos forced in at the end of each coil. 

The use of rheostats on alternating current is extremely 
bad practice. It is entirely unnecessary and very wasteful. 
Where alternating current is used, rheostats should be re¬ 
placed with low voltage transformers, (see Page 544) or 
better still with a motor generator set (see Page 443) or 
mercury arc rectifier (see Page 515), 


428 


HANDBOOK OF PROJECTION FOR 


If, however, it is for any reason necessary to use resistance 
in A. C. projection circuits, we would by all means advise the 
use of the grid type, since they will be less noisy and there 
will be less inductive effect than with coil rheostats. 

RHEOSTAT WASTEFUL.— The rheostat as applied to 
the projection circuit, is for the purpose of consuming the 
difference between line voltage and arc voltage. Put in 
electrical terms it is to “break down” the line voltage to the 
value of arc voltage. In still other words it is to reduce the 
voltage to the pressure necessary to force the desired num¬ 
ber of amperes against the resistance of the arc. 

This process represents an absolute waste of energy, since 
the difference between the line voltage and the arc voltage 
must be and is dissipated in the form of heat generated by 
the resistance, and since the heat cannot ordinarily be put 
to any practical use it follows that the energy consumed in 
its production is wasted, and the energy thus consumed is 
all registered on the meter, and must be paid for. 

For example, let us assume a current supply of 110 volts 
and that we are using 40 amperes at the arc. Voltage multi¬ 
plied by amperes equals watts, hence 110 x 40 = 4,400 watts 
registered by the meter. The voltage of a 40 ampere arc, 
using modern carbons, would be about 50 (see Page 395), 
hence the difference between 110 volts and 50 volts, which is 
60 volts, must be consumed in the resistance element of the 
rheostat. It therefore follows that under this condition the 
waste in the rheostat will be equal to 60 volts x 40 amperes, 
2,400 watts. We therefore are using a total of 4,400 watts, 
and only actually employing 4,400 — 2,400 = 2,000 watts in 
the production of light. Under this condition the rheostat 
is a little less than 46 per cent, efficient. 

The condition just described is bad enough, but if the 
voltage be higher, as for instance 220, then the proportion of 
waste becomes literally enormous. Using 40 amperes from 
220 volt lines through rheostats means a total consumption 
of 220 x 40 = 8,800 watts registered by the meter, whereas 
the actual wattage used at the arc is, as in the former case, 
50 x 40 = 2,000, hence there is wasted in the resistance of 
the rheostat 8,800 — 2,000 = 6,800 watts, or about 3 l / 2 times 
as much energy as is actually employed in the production of 
light, and the rheostat is, under this condition, less than 23 
per cent, efficient. On the other hand, if the voltage weit 
only 60 or 70 then the waste in resistance would be cor¬ 
respondingly less. 

Note: It may be observed that the resistance of an arc 


MANAGERS AND PROJECTIONISTS 


429 


operating off 220 volt lines through a rheostat is higher, 
hence its wattage consumption is higher. This may be true 
but the total waste of energy is not affected by that fact. 

Rheostats are only suitable for use on projection circuits 
where the supply is direct current and the voltage be such 
that the waste inherent in the rheostat is less than the waste 
inherent in a motor generator set. If the pressure be 220 or 
higher it will be very much more economical to break down 
the voltage by means of a motor generator set, and the 
efficiency of modern motor generator sets, or some of them, 
is such that it may pay to use them on 110 volt current, but 
in this we must consider the actual efficiency of a motor 
generator set and the fixed charge of the interest on the 
capital invested, as well as the deterioration of the machine 
itself. If these various items are such that there is not 
sufficient saving as against the rheostat to justify its in¬ 
stallation and operation, it therefore follows that the rheo¬ 
stat, although enormously wasteful, is still the most econom¬ 
ical thing available, everything considered. 

If the current be A. C., then as we have already said, there 
is no excuse for using a rheostat, because either a motor 
generator set or a transformer is available, and of late years 
A. C. to D. C. motor generators have been invented which 
operate at arc voltage, without any resistance in series be¬ 
tween the generator and the arc. Such sets work at maxi¬ 
mum efficiency, and there is the added enormous advantage 
of having direct current at the arc. Also there is the mer¬ 
cury arc rectifier available, see Page 515. If for any rea¬ 
son it is deemed inexpedient to install a motor generator set, 
then a low voltage transformer (inductor, economizer, com- 
pensarc, etc.) may be used, and these devices are very much 
more efficient than the rheostat (their efficiency is well 
above 90 per cent, though they have the disadvantage of 
supplying alternating current to the arc. See Page 544. 

RHEOSTAT CONNECTIONS AND RESULTANT AMP¬ 
ERAGE. —In Fig. 138 we see a 110-volt adjustable-grid rheo¬ 
stat, with part of its casing removed, and a Powers 110-volt 
non-adjustable coil rheostat. The grid rheostat has a 40- 
ampere maximum capacity, which may be reduced to 25 
amperes by means of the dial switch. The Powers has a 
maximum capacity of 25 amperes, which cannot be changed. 
By tracing the connections and comparing them with Figs. 
136 and 137 you will find that it is a multiple connection, so 
that we will get 25 amperes through the Powers and 25 to 40 


430 


HANDBOOK OF PROJECTION FOR 


through the grid, according to how the dial switch is ad¬ 
justed. We will therefore have a total of from 25+25=50, to 
25+40=65 amperes at the arc with this combination. Were 
we to connect the same two rheostats in series on D. C. the 
resultant current would be from 10 to 12+ amperes. It is 
figured as follows. The Powers is a 25-ampere 110 volt in¬ 
strument, hence it has, roughly, (110— 50 )-+- 25 = 2*4 ohms re¬ 
sistance. The grid, when working at 25 amperes, must have 
the same resistance, hence there will be a total of 2^4+2j4 
ohms resistance when they are opposed to the voltage in 
series when the grid is delivering its minimum amperage. 
The resistance of the arc will be approximately two ohms, 
hence ll(H-(2j4+2k2+2) will equal the amperage. This 
amounts to about 16 amperes. If the grid were set on the 




Figure 138. 


40-ampere contact, we would then have (110—50)-^-40= prac¬ 
tically 1.5 ohms, which added to the resistance of the Powers 
makes 2J4+1 /4 = 4 ohms. We would then have 110-r-(2}4+ 
l/4+2)=18+ amperes delivered. If the current were A. C. 
we would then have the same thing, except that instead of 
subtracting 50 from 110 we would subtract the resistance of 
the alternating current arc, which might be taken at about 


30. 


Our readers should understand, however, that these figures 
are approximate only. It is impossible to figure the matter 
accurately, for the reason that the arc resistance varies with 
the length of the arc, also the rheostatic resistance varies 
with (a) temperature of the coils or grids; (b) with their 
age; also merely because a rheostat is stamped “110 volt 25 
ampere” it does not follow that it has exactly the resistance 
this would indicate. Then, too, the supply voltage may not 
be just what you think it is, hence it follows that the results 











MANAGERS AND PROJECTIONISTS 


431 




Figure 139 























































































432 


HANDBOOK OF PROJECTION FOR 


obtained by figuring rheostat resistance will in the very 
nature of things be only roughly approximate. 

As a matter of fact a wire coil rheostat rated at a given 
amperage, and which delivers that amperage when it is- new, 
will not do so after it has been used for a time. The resist¬ 
ance of the wire coil rises gradually for a time, after which 
it remains practically stationary until the coils finally give 
out entirely. When the resistance reaches its highest point 
it will usually be found that the actual delivery of the rheo¬ 
stat will be from 5 to 10 per cent, less than the rated de¬ 
livery. 

This latter may or may not apply to any considerable ex¬ 
tent to cast iron grids. It is claimed that the resistance of 
cast iron remains practically constant. We have been un¬ 
able to secure reliable data substantiating the claim. 

ADJUSTABLE RHEOSTAT AS IT IS.— In Fig. 132 we 
have the photographic representation of the single grid of a 
grid rheostat, and the photographic representation of the 
single coil of a wire coil rheostat. At the top in Fig. 139 we 
have a side and bottom view of a grid rheostat, the grids of 
which are numbered consecutively from 13 to 26. This par¬ 
ticular rheostat is out of date, but it serves very well to 
illustrate what we have in mind. It will be observed that 
between each grid at the top is a spacing washer. These 
washers are alternately lettered X and O. The X washers 
are current carrying (metal) and form an electrical connec¬ 
tion between two adjoining grids. The spacing washers, O, 
are of insulating material. They insulate adjoining grids be¬ 
tween which they are placed from each other at that end. 
The nut on the end of the long bolt which clamp the whole 
thing together is numbered 4. This bolt is insulated from 
the metal of the grids. At the bottom is a similar bolt, also 
numbered 4 and also insulated from the grids. At the bottom 
of the grids are similar spacing washers-, but if there is a 
metal spacing (X) washer (current carrying) between two 
grids at the top there will be an O (insulating) spacing 
washer between the same two grids at the bottom. 

Examining this arrangement in detail we see that, starting 
at the bottom of the left hand outside grid the current 
passes up through the “wires” of the grid (a grid is, as you 
will see in Fig. 132, really nothing but a cast iron wire) to 
the top, through washer X into the second grid, down 
through this grid, through the current carrying washer be¬ 
tween it and the third grid, up the third grid, across the 


MANAGERS AND PROJECTIONISTS 


433 


current carrying washer into the fourth grid, down which 
it flows, and so on through all the grids. 

The connections of such a rheostat are as follows: 11, 8 
and 9 are the binding posts. Usually there are but two, but 
in this case there are three. The reason for the third post 
will be explained further along. Between binding post 11 
and post 6 of the dial switch is a copper wire connection in¬ 
dicated by dotted line 12. The current passes from binding 
post 11 along this wire to post 6 of the dial switch, along 
lever 7 of the dial switch and into the contact the lever of 
the dial switch is on at the time, whence it flows into the 
grids of the rheostat as follows: If the dial switch is on 
contact 1 (the left-hand contact) the current will flow 
through the switch, through contact 1, into and along the 


C-C=TOP OF COILS 
A = RHEOSTAT FRAME 
B= BOLT 

SHADED PART= MICA 
INSULATION 



Figure 140. 


wire into binding post A, which connects with grid one, 
whence it must follow its appointed path through all the 
grids, if the other wire is connected to binding post 9, which 
connects with the bottom of the right hand grid at binding 
post G. Binding post 9 is for use on the voltage the rhe’ostat 
is designed for. Binding post 8 is designed for use where 
the voltage of the current is a little lower than the rheostat 
is supposed to be used on, for instance, 100 instead of 110. 
It connects, as will be seen, with binding post F. If the con¬ 
nection be made to binding post 8 it has the effect of per¬ 
manently eliminating the two right-hand grids, thus lower¬ 
ing the value of the fixed resistance of the rheostat. 

Suppose the switch is on contact 1 and the projectionist 
desires to increase his amperage. He moves the switch to 





















434 


HANDBOOK OF PROJECTION FOR 


the right to contact 2. The wire from contact 2 connecting 
to binding post B which, as you will see, operates to “cut out” 
the two left-hand grids, thus reducing the resistance of the 
rheostat as a whole. Contacts 3, 4 and 5 of the dial switch 
connect respectively to binding post C, D and E. The whole 
thing is diagrammatically represented in Fig. 131. 

In order to disassemble a rheostat of this type one must 

A 

—\ 

-A 


first remove the outer casing, which is held to the frame by 
a number of screws, then the wires connecting to binding 
post A, B, C, D, E, F and G should be disconnected and a 
properly marked tag tied to each, so that no mistake will be 
made in reassembling. The dial switchboard may then be 
taken off by removing screws H-H. Following this the 
whole grid bank must be removed from the frame, and nuts 
4-4 be removed, after which the grids may be disassembled, 
but great care should be taken not to injure the insulation. 

The projectionist will do well before disassembling a grid 
rheostat to have at least one new insulating barrel for bolt 
4, and some new insulating spacing washers. 

The fixed resistance grid rheostat offers no different prob¬ 
lem of construction, except that the dial switch and its con¬ 
nections are absent. The grids are insulated from each other 
in precisely the same way, binding post A-G being the only 
two such a rheostat will have. 

At the bottom in Fig. 139 we have a view of the bottom of 
the rheostat shown above. Such a rheostat may or may not 
have the sides of its individual grids supported by a stiffener, 
which is made of sheet steel lined with asbestos and is slipped 
on the side of the grid to strengthen the grid. 

At Z in the lower half of Fig. 139 we see the spring contact 
of the dial switch. It is esential that spring Z make good 



Figure 141. 









MANAGERS AND PROJECTIONISTS 


435 


electrical contact with contacts 1, 2, 3, 4 and 5. This spring 
should have the attention of the projectionist occasionally, 
since it is subject to some heat and the tendency of the con¬ 
tact is to weaken. Its pressure may be increased by bending 
the spring. It is important that the face of the spring and 
the face of the contacts be kept smooth and perfectly clean, 
by occasionally polishing with No. 00 sandpaper. 

DISASSEMBLING WIRE COIL RHEOSTATS.— While 
mechanical methods may differ, the general method of in¬ 
sulation and the principle involved is clearly shown in Fig. 
140. The upper and lower ends of coils a, b, c, d, etc., Fig. 
131, are joined together, and by the same means are bound 
to the supporting frame, as shown in Fig. 140. To release 
any one coil it is only necessary to remove bolt B, which 
holds its top, and a similar bolt which holds its lower end, 
but before re-assembling be very sure you have not dis¬ 
turbed the insulation, or if you have, that you have re-estab¬ 
lished it in perfect condition. 



CAUTION. —You may find the actual mechanical means 
employed to join and support the coils, and to insulate them 
from the frame, to be different from that illustrated in Fig. 
140, but be assured it is a mechanical difference only. The 
actual thing accomplished is precisely the same as that 
shown, viz.: the coil ends are electrically joined, and in such 
way that they are bound to and supported by the frame, also 










436 


HANDBOOK OF PROJECTION FOR 


they are thoroughly insulated from the frame, either by 
mica or asbestos, usually the former. 

RHEOSTATS FOR ROAD USE.— As between the grid and 
wire coil rheostat we would advise the wire coil for road 
use. This advice is based on the fact that by comparison the 
wire coil rheostat of given capacity is very much lighter in 
weight, little if any more bulky, and is much less liable to 
damage through heavy jars. For road use the Nicholas 
Power Company puts out the wire coil rheostat illustrated in 
Fig. 141. This rheostat is made in two sizes, the smaller 
designed for 110 volts or less, while the large size may be 



used on any voltage up to 240. Both these instruments are 
adjustable. The 240 volt rheostat is quite flexible, in that it 
consists of two separate and distinct banks of coils, con¬ 
nected by a jumper as per Fig. 142, either or both of which 
may be used separately, or the two may be connected in 
series or in multiple. 

Fig. 142 is the diagrammatic representation of this rheostat 
connected in two ways. The position of the adjusting lever 
in A places the two banks of resistance in series for use on 
240 volts. The dial switch post in the center is connected 
directly with right hand binding post by means of a copper 
wire. As the lever is in diagram A, Fig. 142, the current en- 






















MANAGERS AND PROJECTIONISTS 


437 


ters one binding post, the right-hand one we will assume, 
passes through the dial switch lever and from it into contact 
No. 1, which connects with one end of the coil banks It 
passes through all the coils of the right hand bank, through 
the jumper and through all the coils of the left hand bank, 
whence it passes to the arc, the end of the last coil (14) con¬ 
necting to left hand binding post. This places the two sides 
of the rheostat in series and makes it available for use on 
current up to 240 volts pressure. In diagram B, Fig. 142, we 
see the two banks connected to the arc in multiple, the cir- 
cuit wire being connected to the jumper, as shown, so that 
each of the two banks of coils become in effect a separate 
rheostat, as per Figs. 137 and 138. This method is, of course, 
not available 
for more than 
110-volt pres¬ 
sure. By its use 
we get the full 
capacity of the 
two banks of 
coils. When 
using either 
one of the con¬ 
nections shown 
at A or B, Fig. 

142, the lever 
must be placed 
on contact 1, 
though unless 
the coils show 

red with the lever on contact 1 it may be moved to 
contact 2, 3, etc., until the coils begin to show red in a dark 
room, to increase current flow. Of course, in practice, the 
wire would not be actually connected to the jumper, as in B, 
but branched, with one branch connected to each binding 
post, the jumper being removed. 

In considering the selection of a rheostat for road use we 
would suggest that you investigate the merits of “New 
Rheostat/’ a description of which follows. 

All projector manufacturers carry rheostats of standard 
size in stock, and can provide rheostats of special design or 
capacity on short notice. 



Figure 144. 


NEW RHEOSTAT. —In 1921 a new resistance unit which 
is ideal for projection work came on the market, the general 





438 


HANDBOOK OF PROJECTION FOR 


plan of which is diagrammatically outlined in Fig. 143, in 
which only the layout of the electrical parts, is illustrated, 
with the casing, supporting frame, etc., omitted. In the dia¬ 
gram, A and B are the main binding posts of the rheostat. 
C and D are two copper bus bars. E E E E are switches, 
which may be either single pole knife-switches, or a dial 
switch. Line G merely represents the slab of insulating 
material which supports the switches. F F F F are conduc¬ 
tors which connect one terminal of switches E E E E with 

bus bar D. The 
four straight 
lines, 5, 6, 7 and 
8, connecting 
the right hand 
end of bus bars 
C and D, each 
represent a sin¬ 
gle coil of re¬ 
sistance wire 
having a ca¬ 
pacity of, in this 
instance, 10 am¬ 
peres. In this 
particular d i a- 
gram, these four 
coils represent 
the fixed resist¬ 
ance offered by 
the rheostat 
when switches 
E E E E a r e 
open. The next 
three lines, 2, 3 
and 4, represent 
10 ampere coils, 
each of which 
connect with 
one of the binding posts of a switch, as shown. With 
these three switches closed, the rheostat would deliver 40+ 
30=70 amperes. The next line, 1, represents a 5-ampere re¬ 
sistance coil, which also connects to a switch. With all four 
of the switches closed the rheostat would deliver 40+30+5= 
75 amperes. The advantage of the 5-ampere coil is that by 
its manipulation the rheostat would deliver anything from 
40 amperes to its capacity, in 5 ampere steps. 



Figure 145. 
































MANAGERS AND PROJECTIONISTS 


439 


In Fig. 144, two of the coils are shown, and the method of 
their mounting is illustrated. To replace these coils it is 
only necessary to release them from the end insulator and 
stretch a new coil around over the insulators. The frame in 
Fig. 144 carries two coils, one on either side. The insulators 
are of porcelain. 

In Fig. 145 we see the general construction of one type of 
these rheostats illustrated, its cover cut in two, and in Fig. 
146 another, the protecting cover being entirely removed. 



Figure 146. 

In Fig. 147 a type of cover is shown which is to be heartily 
commended. It provides for connecting the rheostat cover 
to the vent pipe, or to the outer air, by means of a pipe, 
thus carrying practically all the heat generated by the rheo¬ 
stat out of the projection room. In the rheostat illustrated in 
Fig. 145 the coils are controlled by a dial switch ; also each 
individual coil is protected by a plug fuse. This has the ad¬ 
vantage that by removing any one of the fuses one coil is 
cut out of service and the capacity of the rheostat reduced 




















440 


HANDBOOK OB PROJECTION FOR 


by that amount. Also, of course, if there is trouble in any 
one individual coil the fuse will blow, thus automatically cut¬ 
ting the coil out of service without injuring any other coil, 
or affecting the rheostat as a whole, except that its capacity 
will be reduced by that amount. 

Let it be clearly understood that any number of coils, or 
coils of any desired capacity may be used. Also any number 

of coils may 
b e controlled, 
either by in¬ 
dividual knife 
switches or by 
a dial switch, 
so that it is 
quite possible 
to have a rheo¬ 
stat with a 
minimum c a- 
pacity of 5 
amperes, and 
a maximum 
capacity up to 
anything the 
supply wires 
will carry. 

Another ad¬ 
vantage is that 
a rheostat of 
more than the 
desired ca¬ 
pacity may be 
ordered, and 
one or more of 
the coils left 

idle, so that in case of accident to one of the coils it is only 
necessary to cut in an idle coil in order to instantly restore 
the rheostat to its normal capacity, and thus permitting of 
repair being made at leisure. 

The rheostats are very light, electrically very flexible and 
are very well ventilated indeed. They are ideal for either 
road or theatre use. They have our hearty endorsement and 
approval. 

As an afterthought we might add that in this type of 
rheostat each coil is, in effect, a separate, individual rheostat 



Figure 147. 



































































MANAGERS AND PROJECTIONISTS 


441 


in itself, which amounts to having a number of 10 ampere 
rheostats, and one 5-ampere rheostat connected together in 
multiple, as will be observed by examining Fig. 143. 


ASK YOURSELF THIS 
QUESTION, BROTHER: 
AM I ONE HUNDRED 
PERCENT. EFFICIENT, 
OR AM I A BULL 
ARTIST AND A “FOUR- 
FLUSHER”? 



442 


HANDBOOK OF PROJECTION FOR 


Current Rectification 

O NLY about 65 per cent, of the theatres of the United 
States and Canada have an available direct current 
supply. The rest have A. C. supply only. We are not 
sufficiently conversant with the situation in this respect with 
regard to other countries in .which this book is used to at¬ 
tempt an approximation of the percentage of theatres having 
A. C. supply only, but no theatres anywhere have a current 
supply the voltage of which is suitable for use at the arc. 

It is a well-known fact that an alternating current projec¬ 
tion arc is not only very much more difficult to handle, but 
also is likely to be more or less noisy (though special A. C. 
carbons have largely reduced the element of noise) also that 
very nearly double the amperage is required at the arc to 
secure an effect equal to a direct current projection arc. In 
other words, to equal the effect of a 40-ampere D. C. projec¬ 
tion arc, an A. C. arc operating at about 80 amperes would be 
necessary. Why this is so is explained on Page 390. 

Due to these facts, the almost universal modern practice 
in large theatres, and the very general practice in smaller 
theatres, is to “rectify” the alternating current supply 
(change it to D. C. and to arc voltage) either by means of a 
motor-generator set or a mercury arc rectifier, either of 
which receives alternating current from the line and delivers 
direct current at the arc, in most cases at arc voltage. These 
machines have been brought to such a state of perfection 
with regard to mechanical construction, efficiency, operation 
and ease of manipulation, that there is now absolutely no 
legitimate excuse for the continued use of alternating cur¬ 
rent at the projection arc. True, the exhibitor may offer in 
excuse the fact that the installation cost of the motor- 
generator or mercury arc rectifier, plus the item of deteriora¬ 
tion, is a considerable sum, but this in fact is no excuse at 
all, because he will get all that and very much more besides 
back in increased patronage of the box office by reason of 
improved screen results. 

This latter is, of course, in a few instances modified by 
the fact that there is an occasional projectionist who is 
sufficiently expert in the handling of the alternating current 


MANAGERS AND PROJECTIONISTS 


443 


arc to produce results very nearly equal to the direct cur¬ 
rent arc. This, however, does not hold good to any consid¬ 
erable extent, and broadly speaking does not in the least 
invalidate our former statement. 

The Projection Department of Moving Picture World 
and the author of this work unqualifiedly recommend the 
installation of either a motor generator set, or a mercury arc 
rectifier, with the notation that modern practice favors the 
motor generator set as against the mercury arc rectifier, 
because of the fact that the motor generator is a very much 
more flexible machine. The motor generator may be tem¬ 
porarily overloaded by as much as 100 per cent., though, of 
course, such an overload could only be maintained for a 
moment or two—sufficient time, however, for change-over— 
whereas the mercury arc rectifier cannot be overloaded to 
any considerable extent; also the motor generator may be 
had in any desired capacity, 'whereas the mercury arc rec¬ 
tifier is not made in anything exceeding 50 amperes capacity. 

Let it be clearly understood that we do not recommend the 
overloading of a motor generator by 100 per cent., even for 
a short time, but such a machine should carry a 50 or even 
a 75 per cent, overload for as much as three minutes, with 
reasonable frequency, without sustaining injury. 

MOTOR GENERATORS. —In the ordinary acceptance of 
the term as applied to projection, the motor generator is 
nothing more or less than an alternating current motor, of 
suitable voltage, cycle and phase to operate on the available 
supply, direct coupled to a direct current dynamo, the latter, 
in latest and best practice, being of the constant current 
type, i. e., wound to deliver an approximately steady amperage 
at considerable variation in arc voltage. 

In fact the latter phase of the matter has been carried to 
such an extent that arc voltage may be doubled without 
appreciably altering the amperage. The latest practice is 
the motor generator, the dynamo of which is so wound that 
when it is “pulling” one projection arc, a second can be cut 
in series with the first, whereupon the voltage of the dynamo 
doubles, the amperage remaining constant. 

The advantage of this type is that with a minimum effort 
on the part of the projectionist the change-over may be 
made without the slightest evidence of the act on the screen. 
This is by reason of the fact that with the arcs operating in 
series, in the very nature of things both of them must and 
will have precisely the same amperage, and if the adjustment 


444 


HANDBOOK OF PROJECTION FOR 


of both, as regards distance from collector lens and angle of 
crater, be the same, and the optical train be identical, the 
screen illumination from each must and will have precisely 
the same value. 

Another plan which has merit is that of the motor gener¬ 
ator having a 70-volt dynamo using ballast resistance to re¬ 
duce the generator voltage to arc voltage. The waste in¬ 
volved is very slight and the plan has its advantages. 

D. C. to D. C. SETS. —There is a special motor generator set 
made, known as the “D. C. to D. C. motor generator,” which 
operates, in effect, merely to reduce the voltage. (See Pages 
466, 468 and 486. 

GENERAL INSTRUCTIONS ON MOTOR GENER¬ 
ATORS. —In the interest of economy of space we shall give 
certain instructions which apply alike to all motor gener¬ 
ators. To incorporate these inThe matter covering each in¬ 
dividual machine would merely oe a reiteration of the same 
thing several times. 

WARNING. —Exhibitors often complain to the author that 
their motor generator set is not as efficient as was claimed 
by the manufacturer. This may very easily be true without 
any fault on the part of the maker, for while a machine in 
perfect condition may show high efficiency, after a few 
months of unintelligent handling, or abuse, it may show 
something very different. Factory efficiency tests are made 
with machines in the very pink of condition. They natural¬ 
ly show very much higher than after a few months under 
the care of a careless or slovenly attendant, or one who 
knows very little and perhaps cares less beyond how to start 
and stop them, and to put fresh oil in the oil wells “once in a 
while.” Loose connections, dirty brushes and roughened 
commutators do not make for efficiency. 

GENERAL INSTRUCTIONS NO. 1, LOCATION.— Several 
things must be given very careful attention when the loca¬ 
tion for a motor generator is considered. 

If it be practical it is decidedly better to locate the motor 
generator in a room directly adjoining and connecting with 
the projection room. If this is not a practical thing to do, 
then it may even be located within the projection room itself. 

A basement location is, for several reasons, objectionable, 
and if the basement be damp and dark it should not be con¬ 
sidered at all. Where there is dampness, the insulation of 
the wires will absorb more or less moisture while the 
machine is idle. This moisture will be expelled rapidly when 


MANAGERS AND PROJECTIONISTS 


445 


the machine warms up, and this, many times repeated, is 
more than likely to do harm. It may, in time, entirely ruin 
the armature and field coils, which would compel the re¬ 
building of the entire electrical part of the machine. An¬ 
other serious objection to this location is that in case any¬ 
thing goes wrong it takes a very much longer time to investi¬ 
gate and make necessary adjustments or repairs than would 
be necessary were the machine located either in the projec¬ 
tion room, or in a room adjoining and connecting therewith. 
Then, too, a dark basement (or other location) compels the 
making of all repairs and performing other necessary opera¬ 
tions entirely by artificial light, which is to some extent ob¬ 
jectionable. Another very, very serious objection with many 
basements is that when the furnace is going there w'ill be 
more or less coal and ash dust in the air, which is bound to 
get into the machine, and in course of time do irreparable 
injury thereto. 

But after all, the most serious objection of all is the fact 
that the machine will be more or less inaccessible to the 
projectionist and will therefore be neglected. It most em¬ 
phatically will not receive the daily attention it ought to 
receive. Common sense should tell anyone that a machine 
which is conveniently located and easily accessible will 
receive more and better attention than if it be located at a 
distance and a more or less inaccessible place. Common 
sense should also tell anyone that lack of necessary atten¬ 
tion means increased deterioration in the machine itself. In 
other words the machine which has proper attention will 
operate with greater efficiency and last much longer than 
one which does not receive proper attention. 

The only legitimate objection to locating machines of this 
kind in or adjoining the projection room lies in the possi¬ 
bility of vibration and noise, or in the weakness of the floor. 
We may, however, dispose of the latter by saying that any 
floor too weak to carry a machine of this kind is entirely 
unfit to be the floor of a projection room. As to the matter 
of vibration, it has, to all intents and purposes, been elimi¬ 
nated in modern machines of this type and such vibrations as 
remains can be entirely absorbed by means of a felt, cork or 
rubber mat, as per instructions under “Installation.” 

GENERAL INSTRUCTIONS NO. 2—INSTALLATION.— 

Upon receipt of a new motor generator the name plate 
should be carefully inspected. If it be a D. C. to D. C. machine 
it is only necessary to make sure that the voltage marked 


446 


HANDBOOK OF PROJECTION FOR 


on the name plate corresponds with the voltage of the sup¬ 
ply. If it be an A. C. to D. C. set it is then necessary to make 
sure the volts, the cycles and the phase of the motor agree 
with those of the circuit to which it will be connected. 

The name plate on the generator should indicate its maxi¬ 
mum capacity. If the machine is to be located in a base¬ 
ment, or at any other place a considerable distance from the 
projection room, the projectionist should make sure that the 
circuits leading from the generator to the projection room, 
and from the main house switchboard to the motor are both 
large enough to carry the maximum current they will be 
called upon to carry with, not to exceed a two-volt, or at 
most a three-volt drop. (See Page 74.) 

If the generator is to be located in a basement it is an 
excellent plan to place it on a foundation raised at least 12, 
and preferably 24 inches from the floor. This is particularly 
important if there is danger of the basement flooding, or if 
the floor is wet, though in either of the latter events it would 
be sheer folly to locate a motor generator set in the base¬ 
ment. 

DROP LIGHT. —No matter where the machine is located 
there should be a drop light hung over it, with sufficient 
slack cord to admit of the light being carried to any part of 
the machine. This latter is especially important if the 
machine be located in a dark place, such as a basement. 

GROUNDING THE FRAME.— The frame of the machine 
should be thoroughly grounded by means of a copper wire, 
one end of which must make good electrical contact with the 
frame arid the other end with a water pipe or the earth, as 
per instructions, Page 346. 

REMOVING SUB-BASE. —If the machine is mounted on 
a sub-base, which for any reason it is desired to dispense 
with, it is highly important that the base which will receive 
the machine be perfectly level, and that the motor and the 
generator be carefully lined with each other. If this latter 
be not perfectly accomplished there will be an undue, and 
possibly a heavy strain on the coupling between the two 
shafts. Imperfect lining of the motor and generator is likely 
to result in noise and vibration; it certainly will cause rapid 
wear of the bearings of both the motor and generator. 
Machines in which the armature of the motor and generator 
are mounted on one shaft, with but three bearings and with 
no coupling between the two armatures, should under no cir- 


MANAGERS AND PROJECTIONISTS 


447 


cumstances be installed without their sub-base, if they be of 
the type which uses a sub-base. 

Where a motor and generator are carried on a single sub¬ 
base or base, it is not necessary that they be bolted to the 
floor, nor is it necessary to build any special foundation for 
them. 

CORK, FELT OR RUBBER.— Motor generator sets in 
which both elements are carried on a single base or sub-base 
require no base, but between them and the floor should be 
one of three things, viz.: a thick pad of cork, a thick pad of 
felt or a thick pad of fairly resilient rubber. These pads 
serve two purposes. They absorb any possible vibration, 
which would otherwise be communicated to the floor, and 
they serve to deaden the noise of the machine. 

Cork is best, but the pad should be two or three inches 
thick. It need not extend all the way under the machine if 
the machine be of the horizontal type. If it be of the vertical 
type it will be just as well to use a pad or mat the full size 
of the machine, and two or three inches more. If the pad be 
of felt it should be of the kind to one inch thick, and four 
or five thicknesses should be used. We can give no advice 
with regard to the rubber pad, because it will depend upon 
the kind of rubber you are able to get, but in any event a 
sufficient thickness should be used to absorb all the vibration. 

It is imperatively necessary that the armature of hori¬ 
zontal type motor generator sets be perfectly level endwise, 
else it will not “float” (have end play), and failure to float 
will probably produce grooved bearings and commutator. 
For this reason it is necessary, after the machine has been 
set on its pad for a week, that it be tested, and if necessary 
levelled by slipping sheets of paper or metal under the low 
end. 

CAUTION— In the case of motor generators the armatures 
of which are joined by a coupling and which are not mounted 
on a single, rigid iron base, the pad method does not apply. 
Such machines must be bolted down to a solid, rigid founda¬ 
tion, the top of which is, of course, perfectly level. 

ELECTRICAL CONNECTIONS.— Wiring diagrams and in¬ 
structions should accompany each machine. It is hardly to 
be expected that the projectionist will be able to make the 
electrical connections for a motor generator, since there not 
only are several different makes, but more than one type of 
some makes; also there are single two and three-phase cur¬ 
rent complications. It is, therefore, to be expected that the 


448 


HANDBOOK OF PROJECTION FOR 


electrical connections of the machine will be made by a com¬ 
petent electrician. 

FINAL PREPARATIONS FOR STARTING.— After the 
machine is installed and the electrical connections complete, 
before starting, revolve the armature by hand and see that 
it moves freely. Examine the armature and commutator 
carefully to see that they are not bruised and that everything 
is in good condition. Examine the face of the brushes and 
test the brush tension. (See General Instruction No. 7.) Let 
the oil out of the oil wells and fill them up with fresh oil. 
(See General Instruction No. 3.) Having taken these precau¬ 
tions, the machine is ready to be tested with current. 

CENTRAL INSTRUCTION NO. 3—OIL.— It may be stated 
as a general proposition that the various largely advertised 
patent oils are absolutely unfit for motor or generator lubrica¬ 
tion. If they be used it is more than likely that there will be 
trouble with the bearings, or a comparatively frequent and 
unnecessary expense for bearing renewals, in addition to 
which there will be a still more serious item, viz.: worn 
journals. 

The character of the oil to be used will depend to a con¬ 
siderable extent upon climatic conditions, but it is safe to say 
that the oil used by the local power plant for lubricating its 
generators will fill the bill. The superintendent of the plant 

will undoubtedly extend the courtesy of telling you what it 



Figure 148. 





MANAGERS AND PROJECTIONISTS 


449 


is; also he probably will be willing to sell you a five gallon 
can at reasonable figures, and a five gallon can should last a 
long time. If you are able to procure the power plant oil 
you certainly cannot do better, because oil used to lubricate 
the heavy generators of a power plant must, in the very 
nature of things, be a good lubricant, and one suitable for 
use on motors and generators. 

If you are unable to procure the oil used by the local 
power plant, then we would recommend for summer use a 
medium heavy dynamo oil, which may be used the year 
round if the motor generator be located in a room that is 
kept warm. If, however, the machine is in an unheated 
place, then in winter time a light dynamo oil will give the 
best general satisfaction. 

BALL BEARING MACHINES.— Some machines are fitted 
with ball bearings, in which case provision is usually made 
for the use of either oil or grease. The amount of oil or 
grease required by a ball bearing is very little, its function 
being more to keep the races and balls free from rust than 
to actually lubricate them. 

It is imperatively essential that only a lubricant containing 
no acid be used with ball bearings. An oil containing, for 
instance, animal fat, will finally roughen the polished surface 
of the balls or races and bring about the final destruction of 
the bearing. For this reason it is very much better that the 
suggestion of the manufacturer of the machine be implicitly 
followed in the matter of selecting a lubricant for its ball 
bearings. 

CAUTION.— Most, if not all, qiotor generator sets of the 
horizontal type have the oil carried up to the journals by 
means of rings which rest on the journal and revojve merely 
by the friction of their own weight thereon. This type of 
bearing is illustrated in Fig. 148, in which we see an oil ring, 
the lower part of which runs through the oil well below the 
journal, the upper part resting on the top of the armature 
shaft, provision being made for this by a slot or groove cut 
in the babbit bearing. At the left it is shown photographical¬ 
ly and at the right diagrammatically. You may understand 
the action of the ring by placing an ordinary iron ring on a 
short piece of iron pipe considerably smaller than the ring 
and revolving the pipe. You will see that the ring also 
revolves, though very much slower than does the pipe. 

Once the action of this kind of an oil arrangement is un¬ 
derstood, two things will be plain, viz.: first, since the lower 


450 


HANDBOOK OF PROJECTION FOR 


half of the ring is immersed in oil, oil will be continually 
carried up to the journal by the ring. Second, if the weather 
be cold and the oil be stiff, then the friction of the journal 
may not be sufficient to revolve the ring, hence the journal 
will receive no lubrication until it has heated up sufficiently 
to melt the oil. For this reason a too-heavy oil must not be 
used in winter if the machine is located in a cold room. 

CAUTION. —Be sure your oil is free from dust or sedi¬ 
ment. Never leave an oil receptacle standing open. If you 
do it will collect dust and its lubricating quality will be 
greatly impaired. Dirty oil very frequently is the cause of 
trouble in bearings, and in any event it wears bearings very 
fast. 

GENERAL INSTRUCTION NO. 4—CLEANLINESS.— It is 

important that all parts of motor generators be kept scrupu¬ 
lously clean. Oil should not, under any circumstances, be 
allowed to collect either on the machine or on the floor near 
it, and the machine should be kept free from dust. A medium 
size hand bellows will be found very convenient for remov¬ 
ing dust from the armature, from around the pole pieces and 
in other inaccessible places. A dirty machine is evidence of 
a lazy, indifferent or incompetent attendant. 

GENERAL INSTRUCTION NO. 5—LOOSE CONNEC¬ 
TIONS. —It is highly important that all electrical connections 
and all bolts and nuts be inspected periodically and tightened 
up, and all electrical connections be kept not only tight, but 
perfectly clean. Loose connections are a continual source of 
unnecessary trouble. 

GENERAL INSTRUCTION NO. 6—AMMETER AND 
VOLTMETER. —Motor generators are, or should be, pro¬ 
vided with both an ammeter and voltmeter, which instru¬ 
ments, in order to serve their best purpose, must be located 
within view of the projectionist when he is in working posi¬ 
tion beside the projector. These instruments should be con¬ 
stantly under the eye of the projectionist. It is a serious 
mistake to locate them where they cannot be read easily and 
continually observed, because there are certain points at 
which the arc furnishes maximum illumination with minimum 
current consumption, and if the ammeter and voltmeter be 
located within plain view of the projectionist, preferably on 
the front wall of the projection room, near the left hand 
projector observation port, the projectionist is very much 
more likely to handle his arc efficiently. This is especially 
true if the arc be hand fed. 


MANAGERS AND PROJECTIONISTS 


45 i 


GENERAL INSTRUCTION NO. 7—CARE OF THE COM¬ 
MUTATOR.— The commutator of a D. C. motor or generator 
should require very little attention, but sometimes it does 
require a great deal. 

The best evidence that the commutator is in first-class 
condition is a sort of glazed appearance, smooth as glass, a 
rather dark brownish shade in color, and a slight squeak 
from the carbon brushes when the armature is revolved 
slowly. To obtain and maintain this condition the following 
care is essential: 

(a) Brushes, set as nearly as possible at the sparkless point, 
which point may, with the old style generator lacking the 
inter or “commutator” pole, vary with the load. On the 
newer type generator the inter or commutating pole is used, 
and the manufacturer marks the point at which the brush 
yoke should be set by making either a chisel or a center- 
punch mark on the yoke and on the frame. Some manufac¬ 
turers fill these marks with white paint so that they are 
very easily seen ; some do not. If these marks are present 
the brush yoke should always be set so that the marks on 
the frame casting and on the yoke coincide or, in other 
words, are opposite each other. 

(b) The brushes must have sufficient tension to make good 
electrical contact with the commutator, remembering that 
every particle of unnecessary pressure will tend to unduly 
wear both commutator and brushes. 

(c) The commutator should be kept clean and free from 
dust. This may best be accomplished by cleaning the whole 
machine every day, blowing the dust out from around the 
field poles, etc., with a bellows, and last of all, wiping off the 
commutator with a canvas pad made as follows : 

Cut a piece of ordinary canvas 6 inches square. "Fold same 
so it is 2 inches wide by 6 inches long, which will form a pad 
with a face of one thickness, backed by two thicknesses. 
Next open up the pad and smear a little vaseline on the cen¬ 
ter section, which is the back side of the face of the pad, 
after which refold and let lie a few hours in a warm place, 
whereupon it is ready for use. 

Sufficient vaseline will gradually soak through the canvas 
to give the commutator all the lubrication it needs, which is 
very little. The foregoing holds good in summer, and in 
winter, too, if the generator is located in a warm room. If, 
however, the machine is cold, then it will be well to moisten 
the face of the pad by using a few drops of a very thin oil on 
a piece of glass, spreading it around evenly and then wiping 


452 


HANDBOOK OF PROJECTION FOR 


it off on the face of the pad, the idea being to get the oil 
evenly distributed on the pad. 

Remember this, however, too little lubrication is better 
than too much, and heavy lubricants (thick oils) must never, 
never, never be used on a commutator. If one application, 
as above, during every six-hour run does not suffice, then it 
is likely that (1) brushes have too much tension, (2) machine 
is overloaded, (3) brushes not properly set, or (4) someone 
has put in the wrong kind of brush, which of course is not 
likely to happen if the machine be a new one just from the 
factory, but is quite possible if it be a second-hand machine, 
or one which has been in a repair shop. 

Never use gasoline or benzine around a commutator; it is 
likely to attack and soften the shellac and insulation, and 
thus set up serious trouble. 

CAUTION.— Where the mica insulation of the commutator 
is- undercut, great care should be taken with regard to lubri¬ 
cating of the commutator. If a soft brush is used no lubrica¬ 
tion at all should be applied. This last caution is necessary 
with undercut insulation, because the lubricating medium 
will have a tendency to combine with carbon dust and fill up 
the space between the commutator bars, thus in time pos¬ 
sibly short circuiting the bars ; also where soft brushes are 
used the brushes themselves, as a rule, contain sufficient 
paraffine to provide all necessary lubrication.. 

(d) See to it that sufficient oil, or combined oil and carbon 
dust, does not collect at any point or spot, either on the 
commutator or the face of any brush, to form a semi¬ 
insulation. 

(e) That there are no high or low bars, and that the com¬ 
mutator is perfectly round. 

(f) That a fragment of copper does not drag across the 
insulation between two adjacent bars, or that oil and carbon 
dust do not form such a bridge. This fault will be 
evidenced by a thin, sparkling ring of light around the com¬ 
mutator. 

(g) That the brush springs do not carry sufficient current 
to heat them. 

(h) That the brushes fit properly in their holders, and are 
kept free from accumulation of dirt, dust, etc. They should 
be taken out, their faces examined, and if necessary cleaned 
at the end of every 60 hours’ run. 

(i) That the brushes are neither too hard nor too soft. 

(j) That the armature of horizontal type machines “floats” 


MANAGERS AND PROJECTIONISTS 


453 


slightly, i. e., has from one-sixteenth to one-eighth inch end 
play, according to size of machine. This tends to prevent 
the brushes from cutting grooves in the commutator, hence 
is very important. Unless the machine sets perfectly level 
the armature will not “float,” hence a level setting is im¬ 
portant. (See “Installation” Page 445.) In vertical ma¬ 
chines in which the armature is carried on thrust ball bear¬ 
ings, the brushes of opposite polarity overlap, so that the space 
between the brushes on the one side is covered by a brush on 
the other. This arrangement causes a very even, uniform 
wear. 

(k) That the copper and mica insulation wear down evenly. 

(l) That the generator is not overloaded, and that there 
are no other faults present which would tend to cause un¬ 
necessary sparking, or otherwise injure the commutator. 

SPARKING. —Should the brushes of the motor or gener¬ 
ator show excessive sparking, it may be attributed to one of 
the following causes: 

(a) If it be a belt driven machine, the belt may be slipping; 
if the sparking is spasmodic or intermittent the trouble will 
probably be found in the belt, since belt slip causes sudden 
variations in speed, and this will, in itself, cause sparking, 
because it has the effect of producing heavy fluctuations in 
voltage. The remedy is to tighten the belt or use a belt 
dressing, and in this connection ordinary black printer’s ink 
is as good an article as we know of to stop belt slipping. 
Ten cents’ worth obtained at any printer’s will last a month 
or more. 

(b) In considering the following remember that if the 
machine is a new one and the rocker arm is set at the posi¬ 
tion marked by the manufacturer, as before explained, the 
rocker should under no condition be shifted, since the entire 
performance of the generator depends, in some cases, on the 
accurate positioning of the brushes. 

Brushes not set correctly, that is to say, the rocker arm 
too far one way or the other; also the brushes may be too 
close together, or too far apart. In the first case the remedy 
is to move the rocker arm until the neutral position is found, 
whereupon sparking will either cease or be reduced to a 
negligible quantity. If this fails to remove the trouble, we 
would see if the brushes themselves are the correct distance 
from each other. In a two-pole machine they should bear on 
the commutator at diametrically opposite points. That is to 
say, the distance from brush-point to brush-point should be 


454 


HANDBOOK OF PROJECTION FOR 


exactly the same when measured both ways around the com¬ 
mutator; in other words, distance A should equal distance B, 
as per upper drawing, Fig. 149. 

If it be a four-pole machine, with two positive and two 
negative brushes (four altogether), the correct distance is 
one-fourth of the circumference of the commutator between 
the points of adjacent brushes; that is to say, distances 
marked X should all be equal, as per lower drawing, 
Fig. 149. If it be a machine with more than two positive and 
two negative brushes (more than four brushes all told), 
divide the number of commutator segments by the number 
of poles or field coils of the machine. The result will equal 



Figure 149 



the distance, in commutator bars, the brushes should be 
apart. 

(c) Dirty brushes or dirty commutator may cause spark¬ 
ing, or may even prevent the generator from picking up its 
load at starting, and will sometimes cause a badly fluctuating 
arc. Some of the causes of dirty brushes and dirty com¬ 
mutators may be found in one of the following: 

Carbon brushes contain a small amount of paraffine. When 
the carbon gets warm, if it be excessive in quantity, it is 
likely to ooze out and coat the commutator thus forming a 
partially insulating coating in spots, or the paraffine may mix 
with dust and coat the end of the brush with a semi-insulat- 




MANAGERS AND PROJECTIONISTS 455 

ing compound. The obvious remedy is to clean the dirty 
parts. 

To clean the commutator, use a brush stiff enough to 
remove any foreign matter which may cling to its surface, 
yet not stiff enough to injure the surface. If the brush will 
not remove the deposit, then use 00 sand paper (NEVER use 
emery paper or emery cloth on a commutator) applying the 
same while the commutator is revolving, but with just barely 
enough pressure to clean the metal. After having cleaned 
the surface, put a few drops of light oil on a cloth, or use 
the pad already described, holding it lightly to the commu¬ 
tator as it revolves. Don’t get much oil on the surface of the 
commutator—just a “suspicion,” as it were. 

If it is a carbon brush which is dirty, or which does not fit 
the curve of the commutator, raise it just enough to slip a 
piece of No. H sandpaper between the brush and commutator, 
with the sand side against the brush, and pull it back and forth 
around the curve of the commutator until enough of the 
brush has been ground away to clean the surface, or to make 
it fit the commutator. This is illustrated in Fig. 150. 

Do this very carefully. If the brush fits loosely in the hole 
it is best to sand in the direction of rotation only, else the 
brush will wiggle back and forth with the sandpaper, thus 
injuring rather than improving the contact. Be sure and 
always clean the commutator thoroughly after doing this, 
since if carbon dust is left adhering to its surface it may work 
into the insulation and cause a local short circuit between 
two bars. 

(d) The brush not making proper contact with the com¬ 
mutator, which may be due to (1) tension spring not strong 
enough; (2) tension spring having lost its temper; (3) brush 
stuck in its holder; (4) brush not fitting the curve of the 
surface of the commutator; (5) brush holder set at the wrong 
angle; (6) high bar or insulation. 

The remedies are: (1) Stretch the spring, if it is a 
spiral spring and in compression, or cut down its length if 
the spring be in tension. If it is not a spiral spring, do what¬ 
ever is needful to make the spring stronger, installing a new 
one, if necessary; (2) put in a new spring and, since the fact 
that the old spring has lost its temper is evidence that the 
spring itself is carrying too much current, reinforce it with 
a current-carrying jumper; (3) the remedy is obvious: do 
whatever is needed to loosen the brush ; (4) use sandpaper, 
as before described, until the brush fits the commutator sur¬ 
face; (5) straighten the holder; (6) see section f, further on. 


456 HANDBOOK OF PROJECTION FOR 

There should, however, be only sufficient tension on the 
brush to insure its making good contact with the commuta¬ 
tor. Be careful, therefore, and don’t get your springs too 
strong. If you do there will be unnecessary wear both on 
the brush and the commutator, which will to some extent 
add the element of mechanical heat generated by undue 

friction. , ,, ,,, 

Reasons for the brush sticking in the holder are: (1) 
Dirt in the holder or on the brush; (2) brush not true; (3) 
hammer that rests on the brush (where that type of tension 
is used) not working true on the slot-end of the brush. The 
brush should slip freely in its holder, though not freely 
enough to allow of any considerable amount of play, and the 
hammer should be so adjusted that it lies true in the slot at 
the end of the brush. A brush which is not true may be 
evened up by tacking No. 1 sandpaper on a perfectly flat 
surface and rubbing the brush thereon. 

(e) Commutator worn too thin. If the commutator wears 
down too much, although it may wear evenly and appear to 
be in good condition, the brushes will spark in spite of every¬ 
thing you may do, particularly when the machine is working 
at capacity. The reason may lie in the fact that since the 
segments are wedge shape, as they wear down they become 
narrower, thus allowing the brush to span more of the cir¬ 
cumference of the commutator than was intended, or there 
may be a slight error in the setting of the brush holder, and 
this error becomes greater as the distance between the brush 
holder and the commutator increases. The only remedy is a 
new commutator, but the sparking may possibly be lessened 
somewhat by moving the brush holder closer to the com¬ 
mutator. This trouble appears at its worst in a series type 
machine. 

(f) A high or low commutator segment. This fault may 
usually be detected by the clicking sound made by the brush 
in passing over the defective segment when the machine is 
run at moderate speed. When the segment is low the brush 
rides in toward the shaft each time the bad bar passes under 
it. If it is high the brush will jump. The remedy will depend 
somewhat upon the cause. It may be that the segment has 
become loose, in which case it may be driven back into place 
by tapping lightly with a wooden mallet, or by using a 
wooden block and hammering gently, but the armature will 
probably have to be taken out and sent to the repair shop 
unless you yourself can tighten the clamp ring—a rather 
delicate operation. 


MANAGERS AND PROJECTIONISTS 


457 


If the segment is high by reason of the fact that, being of 
harder material than its mates, it has worn down more slow¬ 
ly, then, using a fine file, it may by very careful work be 
dressed down. If, on the other hand, it is low, then the only 
remedy is to turn down the rest of the bars to match. 

If the fault is slight, this may be done by removing the 
brushes and holding a piece of grindstone which has been 
turned out to fit the circumference of the commutator to it 
while it is revolved rapidly. This process is, however, slow. 
The best way is to put the armature in a lathe and turn it 
off. In the case of a motor the grinding may, however, be 
done with the brushes down and the machine running by its 
own power, but if this be attempted it must be done with 
great caution. 

When you are through, the face of the brushes should De 
thoroughly cleaned by drawing No. Yz sandpaper drawn 
around the curve of the commutator with the sand side next 
to the brushes as per Fig. 150, in order to grind off their 
face and thus remove any particles of sand which may have 
become imbedded in the brush, since such particles would 
scratch the commutator and cause undue wear. It is better 
to do the grinding with the brushes raised and the machine 
run from some outside source of power, if it is practicable. 

(g) A rough or eccentric commutator. This may be caused 
by improper care, or by the use of defective materials in its 
construction. A rough commutator may be detected merely 
by feeling. The mica insulation between the segments will 
either stand out in ridges or be worn down so that there is a 
small groove between the segments. An eccentric commu¬ 
tator may most readily be detected by holding some instru¬ 
ment firmly against the frame opposite the commutator so 
that its end just touches the bars. 

If the commutator is true it will touch all the way round 
as the armature is slowly revolved, but if the. commutator 
is eccentric it will, of course, only touch the high spots. If 
the eccentricity be bad it will cause the brushes to move in 
and out of their holders perceptibly when the armature is 
revolved slowly. The only remedy is to turn the commutator 
down, and this can only be successfully done in a machine 
shop where work of this character is understood. 

In preparing to turn down a commutator the machinist 
should note whether the journal or bearing points run true 
when the armature is revolved on its centers in the lathe. 
Often the centers themselves are not true with the journals, 
due to a defective center or a sprung shaft. In either case if 


458 


HANDBOOK OF PROJECTION FOR 


the shaft be swung on its centers in the lathe the commuta¬ 
tor will show eccentric. A competent machinist will, of 
course, know what precautions to take in a case of this 
kind. 

(h) Brushes having too high resistance, the evidence of 
which is that they get very hot and slowly crumble away 
at the end next the commutator. The remedy is to get good 
brushes. 

(i) Low bearings. In some types of machines low bearings 
will throw armature out of center sufficiently to distort the 
magnetic field, which will cause sparking. The evidence of 
this fault is that the air gap between the armature and the 
pole piece is smaller at the bottom than at the top. The 
only remedy is to replace the worn bearings with new ones. 

(j) Short-circuited armature coil. This trouble may cause 
the voltmeter to fluctuate badly and the shorted coil to heat 
very quickly. The coil may be shorted within itself, or 
there may be a connection between two adjoining commu¬ 
tator segments. Remedy: Locate and remove the short. 

(k) A reversed armature coil. This may be located by 
holding a compass over each coil of the armature in turn, 
and sending a few amperes of direct current through the 
coil, with the brushes raised and resistance in series to limit 
current flow, or current from a battery may be used. The 
coil which causes the compass to turn in the opposite direc¬ 
tion from its mates is the guilty party. The remedy is, re¬ 
verse the connection or direction of the windings of the 
defective coil. 

(l) A bent armature shaft. This of, course, will cause the 
whole armature to wobble. The only practical remedy is a 
new shaft. 

(m) Overload. The most prominent symptom of overload 
is the armature heating all over. Sparking may be lessened 
but not entirely stopped by moving the brushes ahead or 
back. By “ahead” we mean in the direction in which the 
armature is revolving. The remedy is obvious. Get a machine 
of larger capacity, or reduce the load on the one you have. 

(n) High speed sparking is caused by the brushes not 
being able to make proper connection with the commutator 
by reason of excessive armature speed. 

(o) A weak field. This may be detected in a generator 
by the inability to pick up readily, and by failure to main¬ 
tain normal voltage. In a motor the starting power is 
decreased, but the speed and current are increased. A weak 


MANAGERS AND PROJECTIONISTS 


459 


field may be caused by (1) a loose joint in the magnetic cir¬ 
cuit; (2) heat may lower the insulation of the field winding 
sufficiently to allow the current to short circuit through 
it; (3) there may be a metallic short in the field coil. 
Remedies: With a voltmeter test across each field coil; the 
one showing the least drop is the defective one. If all read 
the same, then there is a loose joint in the magnetic circuit. 

(p) A shaky foundation, or anything else that causes vi¬ 
bration in the machine, may and probably will set up the 
commutator sparking. The only remedy is to eliminate the 
vibration. 

Should a ring of fire develop, or something that looks like 
a ring of fire around the commutator, it may be caused by 
(a) a piece of copper pulled across the insulation between two 
bars; (b) an open circuit in the armature. 

In the first instance the ring will not be strong, but just a 
thin sparkling streak of light around the commutator. The 
remedy is to remove whatever is causing the short between 
the bars, which can usually be done by holding a piece of 
fine sandpaper lightly to the commutator, though the right 
way is to stop the machine and hunt up the trouble, using 
a magnifying glass, if necessary. 

An open circuit in the armature might be caused by a break 
in one of the armature wires itself, or in one of its connec¬ 
tions with the commutator, and these in turn may be caused 
by excessive current burning off one of the wires; or a nick 
in one of the wires may be the seat of the trouble, or the 
commutator may become loosened and break off one or more 
of the leads. The defect may be readily located, as the mica 
will be eaten away from between the commutator segments 
to which the faulty coil is connected, and the segments 
themselves will become full of holes and burned at the edges. 

If this trouble is caught in time, the “open” may be closed 
and the commutator turned up true. Sometimes, by reason 
of carelessness, abuse or overload, the armature becomes 
hot, which causes the solder on the connections between 
the coils and commutator bars to soften, whereupon centrif¬ 
ugal force will throw it out, and there will, of course, be 
trouble, though there may be no complete opening of cir¬ 
cuits. The action, however, so far as the ring of fire be 
concerned, is the same as if there were, and the commutator 
bars will become blackened and pitted and their edges burned. 
But if any of the foregoing faults be caught in time they 
can be remedied; if not, it will be necessary to install a new 


460 HANDBOOK OF PROJECTION FOR 

commutator, and perhaps a new armature coil or coils as 
well. 

GENERAL INSTRUCTION NO. 8. —Before starting the 
machine see that it is perfectly clean and that the brushes 
move freely in their holders and make good contact with 
the commutator. Also make sure that all connections are 
tight. 

GENERAL INSTRUCTION NO. 9.— Bearings run hot. The 

first rule when a bearing runs hot is to see that the oil well 
is filled with good clean oil and that the oil-rings run freely, 
carrying the oil to the shaft. If a bearing runs hot on a new 
machine, shut down and wash it out with kerosene. The 
trouble is probably due to dirt that has accumulated in ship¬ 
ment. If the bearing has been running along satisfactorily 
and suddenly gets hot, flood the well with clean oil, leaving 
the drain cock open and pouring in the clean oil while the 
machine is running, to free the bearing from. dirt. A change 
to a different grade of oil, either heavier or lighter, will 
often correct a bearing trouble of this kind. Never use water 
to cool a bearing. It may get into the insulation of the wind¬ 
ings and cause worse trouble A machine with clean oil 
of the proper grade never gives trouble from hot bearings. 

GENERAL INSTRUCTION NO. 10.— Heating. Many pro¬ 
jectionists, who handle motor generator sets and are not 
posted as to the permissible operating temperatures of same, 
become alarmed when some part or parts of the apparatus 
feel very hot to the .touch. 

The fact that a motor or generator, or parts thereof, feel 
quite hot to the touch does not necessarily indicate an unsafe 
condition. 

To determine the actual state of affairs, proceed as follows: 
The projection room should be equipped with a good ther¬ 
mometer with a centigrade scale, though a Fahrenheit scale 
can be made to serve, provided it will register not less than 
200 degrees. 

The American Institute of Electrical Engineers advises, in 
its standardized rules, a permissible maximum actual tem¬ 
perature of 90 degrees C, which is equal to 194 degrees Fahr., 
as the limit of safe operating temperature for motor or 
generator parts, or for transformer coils, et cetera. This means 
that inasmuch as the ordinary temperature of the human 
body is about 98 degrees Fahr. (blood temperature) 194 
degrees Fahr. would be very hot to the touch. 


MANAGERS AND PROJECTIONISTS 


461 


The right way to measure the temperature of a part is to 
bed the thermometer bulb in a ball of rather stiff putty, and 
then place the putty against the suspected part, leaving it a 
sufficient time for the putty to get as hot as the part is. 
This will cause the thermometer to accurately register the 
temperature of the part. 

Roughly, as applies to projection rooms, we may say that 
any part that is not more than 50 degrees C. (90 degrees 
Fahr.) higher than the actual temperature of the room, is 
not exceeding the above named limt, and unless this limit 
be exceeded, the equipment will not be damaged. 

NOTE.—To reduce Centigrade to Fahrenheit (C. to Fahr.) 
multiply the degrees Centigrade by 1.8 and then add 32. For 
instance, assuming a temperature of 40 degrees C., how 
much is it Fahr.? 40x1.8=72 and 72+32=104 degrees. 

THE HERTNER TRANSVERTER.— The transverter 
needs no introduction. It is giving service in projection 
rooms all over this and other lands. It is of the “upright” 
type, in that its armature stands vertical, with the D. C. ele¬ 
ment at its upper end. 

The generator is of the shunt wound commutating pole con¬ 
stant current type, the double arc machine being designed 
to maintain practically constant amperage under a variation 
of from 50 to 130 in voltage. In practice this means that 
the generator voltage rises from its normal of between 50 
and 60 volts when one arc is operating, to from 100 to 130 
volts when two arcs are burning, without causing any change 
in amperage. This is accomplished without the use of any 
resistance in series with the arc, the maintenance of constant 
amperage under variation in voltage being entirely auto¬ 
matic. 

The motor is mounted in the same frame with, and immedi¬ 
ately beneath, the generator. The motor and generator arma¬ 
tures are mounted on separate shafts, which same are coupled 
together in the following way: One half a flange coupling 
is fitted to the upper end of the motor armature shaft, and 
the other half to the lower end of the generator armature 
shaft. The hub of the fan which supplies ventilation is 
placed between the two halves of the coupling, and the whole 
is clamped together by bolts, so that the assembled unit, as 
a whole, comprises the generator armature (at the top), the 
fan between and the motor armature below, the power from 
the motor being transmitted to the generator armature by 
means of the coupling, which latter is so made that it can be 


462 


HANDBOOK OF PROJECTION FOR 


readily disassembled, thus providing for the easy removal of 
the generator armature, should it become necessary in order 
to turn up the commutator or make other repairs. 

BEARINGS. —In the base of the machine is both a radial 
and a thrust ball bearing, Fig. 151, the latter carrying the 
weight of the combined armatures and fan. The center frame 
section carries a radial bearing, Fig. 151, and there is a radial 
bearing at the upper end of the generator armature shaft, 
Fig. 151, so that the armature is very well supported. The 
bearings are all ball bearings, and they are all arranged .for 
grease lubrication. 



Annular bail bearing in .boosing. 


\ Commutator extra heavy bant 
} drawn copper bars. 


i Covers, Protect commutator and 
j brushes. Permit ventilation 
( and inspection. 


C. Armature, Made up > of 
7 laminated steel core having 

} form wound coils firmly era- 

’ bedded in its slots. 

- Centrifugal fan. Keeps windings 
I cool and dean. Draws fresh air 

\ in through motor and generator 

j and discharges it through open¬ 

ings in center section. 


Flanged Coupling. Joins DC 
armature and AC rotor shaft. 


\ Annular ball bearing and thrust. 
) bearing in housing. 


Cup. 


t Annular ball hearing ■ in hous- 
I trig gives support to shafts in 
l ' center of machine. 


Rotor end ring formed by weld¬ 
ing the ends of the rotor bars 
in»"o a solid nut**. Indestruc¬ 
tible, • 


Wi to 19! j inches 


Figure 151. 







MANAGERS AND PROJECTIONISTS 


463 


CAUTION.—Grease for lubrication should be very care¬ 
fully selected. It must be not only entirely free from graphite 
and acid, but also free from any elements which would in 
time form acid, because acid destroys the surface of the steel 
halls and the runways, causes pitting and works havoc. For 
these reasons we emphatically recommend that grease for 
use with the Transverter be purchased from its manufac¬ 
turer, the Hertner Electric Company, Cleveland, Ohio. 

The parts are shown in the phantom view, Fig. 151, which 
also gives the over-all dimensions. It will be observed that 
the diameter varies very little, only the height altering in 
machines of different capacities. 

The Transverter is supplied with either one of two types 
of panel, termed “Panel A” and “Panel B.” These consist of 
an inclosed steel cabinet on which is mounted a field rheostat 
for the generator, by means of which the projectionist 
may vary the current from somewhat above to somewhat be¬ 
low normal. The panel also carries a voltmeter and ammeter 
for the arc circuit. The only difference in the two panels is 
that panel B carries two quick-break switches to be used in 
making change-over. It is for the two-arc machine. 

The manufacturer’s claim is that the Transverter should 
require no attention beyond keeping it reasonably clean, put¬ 
ting grease into the bearings as required, and renewing the 
brushes when necessary. This may be quite true, in a general 
way, but we would nevertheless advise the projectionist to 
examine the machine carefully, at set intervals, because that 
machine never was and probably never will be made which 
will not require more or less expert attention. 

DON’T ROCK BRUSHES. —The rocker arm should never 
be moved, because the performance of the Transverter de¬ 
pends very greatly upon the correct setting of its brushes. 
This adjustment is very carefully and accurately made at 
the factory, and the correct position of the rocker arm is 
marked. If after putting in new brushes the characteristics 
of the machine seem to be altered, it indicates merely that 
the brushes are not making proper contact with the commu¬ 
tator. The fault will correct itself in time, or it may be 
immediately corrected by inserting a piece of No. 1 sandpaper 
between the brushes and commutator, one brush at a time, 
sand side next the brush, and with the full tension on the 
brush, drawing the sandpaper back and forth around the 
commutator until the brush face is ground to fit the curve of 
the commutator surface. See Fig. 150, Page 454. If brushes 


464 


HANDBOOK OF PROJECTION FOR 


are loose in their holder, draw sandpaper in direction of ro¬ 
tation only, since if' you draw it both ways the brush will 
wiggle back and forth and will not fit the commutator. 

Transverters are made for all commercial frequencies of 
current, for all commercial voltages, for single and two or 
three phase, and with an output capacity of from 35 to 125 
amperes. 

DOUBLE ARC INSTALLATION INSTRUCTIONS.— 

Transverters should be set on a floor which is entirely free 
from vibration. It is not necessary to bolt them down. Set 
the machine on the four cork pads which come with it. Its* 
weight will hold it in place. 

WIRING. —Make connection from the A. C. line service to 
the starting switch, and from the starting switch to the motor 
terminals, as shown in Fig. 152. Having done this, close 
starting switch and make sure the armature rotates in the 
direction indicated by arrow on top cap of machine. If, in 
the case of two or three-phase supply, the armature rotates 
in the wrong direction, it must be reversed by reversing one 
of the phases of the motor. 

CAUTION.—Do not attempt to change direction of rota¬ 
tion or polarity by changing connections inside the machine. 

The machines are all checked up complete, together with 
their equipment, when tested. The motor must be connected 
to proper side of the line, and connections to panels must be 
made correctly in order to bring polarity of instruments 
and lamp right. 

FUSES. —Fuse the A. C., or motor side of these machines 
only. The D. C. side does not require fuses or switches, other 
than those shown in wiring diagram. The fuses at motor 
starting switch must be large enough to carry the maximum 
load of the machine. Manufacturer’s instructions, which ac¬ 
company each transverter, will give the proper size of fuses 
for each machine. 

WIRING TO LAMPS. —Use wire of sufficient size to carry 
the rated D. C. amperage from point L on Transverter to point 
A on panel board, Fig. 152. No. 12 or No. 14 wire may be used 
to connect point F on Transverter to point F on panel board, 
Fig. 152. 

OPERATING INSTRUCTIONS.— Before starting motor, 
have lamp carbons separated and projector table switches open 
Close motor starting switch. Close short circuiting switch 
which controls lamp you do NOT wish to use. Allow suffi- 


MANAGERS AND PROJECTIONISTS 465 

cient time for generator voltage to build up before attempt¬ 
ing to strike an arc, say 15 seconds from time of starting 
motor, then bring carbons together, instantly slightly sep¬ 
arating them again. As the carbons heat up, gradually 
separate them until the proper arc length is had, whereupon 



Figure 152. 


the voltmeter will show 55 volts, provided the carbons be of 
correct size and correctly set. Any desired change in am¬ 
perage, within the range of the machine, may be made by 
changing the position of the field rheostat regulator, but it 
must be remembered that the regulator provides means for 
obtaining amperage in excess of the rated capacity of the 
machine, which excess should not be used continuously. It is 
intended only to provide excess current for use where a tem¬ 
porary excess of light is desired by reason of a very dense 
film, or by reason of heavy tinting. The regulator also pro¬ 
vides means for obtaining a less amperage than the rated 
capacity of the machine. If the projectionist will take advan¬ 
tage of this provision he will not only improve his work, but 
will also effect a considerable saving in light bills. 











































406 


HANDBOOK OF PROJECTION FOR 


TO STRIKE A SECOND ARC. —Assuming one projector 
to be already in operation, adjust its arc to a 55-volt length, 
then bring the carbons of the idle lamp into contact, and, 
still holding carbons of idle lamp in contact, open panel 
board short circuiting switch controlling that lamp. When 
switch is open, Instantly, but slowly separate carbons, in the 
manner already directed for a single arc. When both lamps 
are in use the voltmeter on panel board will indicate the 
combined voltage of both arcs, which should read between 
105 and 120 volts, probably about 110. 

To “kill” either arc it is only necessary to close the panel 
board switch controlling that lamp. This in no way affects 
the remaining arc. 

GENERAL CARE. —Keep the machine clean. Do not use 
sand or emery paper on commutator. Should the commuta¬ 
tor become dirty, hold a piece of coarse canvas or cheese 
cloth firmly against its surface while machine is running, and 
when free of dirt, wipe the surface with a clean cloth pad, 
moistened very SLIGHTLY with pure vaseline. See Section 
C general instructions No. 7. 

Do not permit the brushes to become too short. If you 
do, disastrous sparking will result. A new set of brushes 
should be put in before the old ones are entirely worn out. 

Instead of putting in a new set all at one time, it is better 
to put in two first, one in each holder, and at opposite ends 
of commutator. Run that way until the new brushes have 
worn to a perfect fit, whereupon you may replace the other 
worn brushes with new ones. 

NOTE. —An extra set of brushes are shipped with every 
Transverter, and no other grade of brush should ever be 
used. 

The three grease cups on the machine should be given one- 
half turn once every two (2) weeks. If this is done these cups 
will require refilling every thirty or forty days. 

When ordering parts from manufacturer always give num¬ 
ber on name plate of the machine. 

D. C. TO D. C. TRANSVERTER.— When the theatre is sup¬ 
plied with direct current at a pressure of 250 volts or more, 
the Hertner Company makes a motor generator set consisting 
of the standard Transverter generator direct connected to a 
D. C. motor. This particular type of machine is made horizon¬ 
tal, instead of vertical. The units are mounted on ball bear¬ 
ings, and are provided with centrifugal fans. 

Where the theatre is supplied with direct current at a 


MANAGERS AND PROJECTIONISTS 


467 


pressure of from 110 to 250 volts, a special transverter has 
been designed, for which the manufacturers claim an effici¬ 
ency of about 80 per cent, when the machine is operating on 
a 220-volt supply, and somewhat higher efficiency when the 
supply is at 110 volts. This machine might be called a D. C. 
auto transformer. It consists of a D. C. armature with a single 
commutator, which is provided with a third set of brushes. 
By a peculiar arrangement or winding of the fields, a constant 
current may be taken off the commutator when constant volt¬ 
age is supplied. 

This machine is vertical in design, and its moving elements 
are carried by ball bearings. It is equipped with the usual 
centrifugal fan. 



Figure 152J4. 

D. C. to D. C. Transverter 

The installation of these D. C. to D. C. machines is in general 
the same as the A. C. to A. C. equipments, with the substitu¬ 
tion of a D. C. motor starter for the A. C. switch or starter, and 
its care is fully covered under the instruction for the A. C. 
transverter. 

GENERAL ELECTRIC COMPENSARCS.— The General 
Electric Company applies the name compensarc to three 
different types of machine, viz.: 

The A. C. to D. C. Motor Generator Compensarc. 

The D. C. to D. C. Motor Generator Compensarc. 

The A. C. to A. C. Projection Transformer Compensarc. 

The General Electric Motor Generator Compensarc, both 
A. C. to D. C. and D. C. to D. C., are horizontal type machines, 
designed for the operation of two projection arcs without re- 



468 


HANDBOOK OF PROJECTION FOR 


sistance in series therewith. The arcs may be operated either 
singly or in series, amperage remaining constant, no matter 
whether one or two arcs are burning. The voltage of the 
generator, however, doubles when the second arc is struck. 
No resistance is used in series with the arc, either when burn¬ 
ing singly or when both are in use. 

The A. C. to D. C. type consists of an A. C. motor and a 
D. C. generator mounted upon a cast-iron sub-base, their 
armature shafts connected by means of a rigid coupling. 

The general appearance of the A. C. to D. C. set is shown in 
Fig. 153, in which the smaller element is the A. C. motor. The 
motors are standard A. C. machines, but the generators are 
wound specially for projection work. These sets are built 



Figure 153. 


in five standard sizes, delivering 35, 50, 70, 100 and 125 amperes 
D. C. to the arc. The A. C. motor may be had for any stand¬ 
ard voltage or current frequency, and for single two or three- 
phase current. The machines are well made and have been 
in use for quite a long while, giving excellent results and 
general satisfaction. 

The appearance of the D.C. to D.C. is shown in Fig. 154. It 
consists of a D.C. motor and a D.C. generator, the armature 
shafts of which are rigidly coupled. They are intended pri¬ 
marily for use on high voltage D.C. current supply, the term 
high voltage being intended to indicate anything from 220 
volts up. These sets and the A.C. to D.C. sets are made in 




MANAGERS AND PROJECTIONISTS 


469 


the same standard sizes. If designed to operate from 110- 
volt supply the matter of electrical efficiency of the machine 
should have very careful consideration, but for 220 volts or 
higher there can be no question as to their being an excellent 
investment. 

Each two-lamp series type motor generator compensarc 
consists of a completely assembled motor and generator and 
a steel cabinet panel for the generator, in which a field 
rheostat is mounted. 

We get an idea of the appearance of this panel in Fig. 155. 
On its face is an ammeter, calibrated only for the operating 
range of the set. 

The black mark 
approximately in 
the center of the 
scale shows the 
normal point at 
which the set 
should be oper¬ 
ated. Other 
marks indicate 
both the high 
and the 1 o w 
operating points. 

Beyond these 
two latter marks 
there is no 
calibration a s 
they represent 
the extreme 
range of capacity Figure 154. 

of the machine. 

The panel is so arranged that the front, carrying the 
rheostat and ammeter, may be removed, the cabinet be put 
in place, all conduit and wiring arranged and then the steel 
front carrying the ammeter and rheostat, put into place and 
connected. This is an excellent plan, in that it protects the 
instruments from any possible damage during installation. A 
door on the side of the cabinet gives access to connections 
for inspection and for test after installation. 

The set includes two S.P.S.T. enclosed knife switches. These 
are the short circuiting switches. They are all ready for 
mounting on the projector, along with the main projector 
table switch and motor drive switch. Closing either of these 
switches has the effect of short circuiting the lamp it controls. 



470 


HANDBOOK OF PROJECTION FOR 


so that no current will pass through the lamp. They should 
be connected ahead of the projector table switch. If this is 
done the idle lamp may be trimmed without opening the cir¬ 
cuit. 


The following are the dimensions data of the steel panel: 




DIMENSIONS IN INCHES 

RATING OF 

AMMETER SCALE 




COMPENSARC 

MARKING 

Height 

Width 

Depth 

Two 35-amp. lamps 

0- 30- 35- 40 

11 

8K 

m 

Two 50-amp. lamps 

0- 40- 50- 60 

11 

8 X 


Two 70-amp. lamps 

0- 60- 70- 80 

11 

8 Y 2 

4 % 

Two 100-amp. lamps 

0- 90-100-110 

17 

12 H 

6 % 

Two 125-amp. lamps 

0-110-125-135 

17 

12M 

6 % 


When one arc is burning the process of starting the other 
is as follows: Close the projector table switch and freeze 
the carbons of the idle lamp. Next open the short circuiting 
switch of the idle lamp and separate the carbons in the usual 
way, except that it should be done very slowly. As the second 
arc is sprung, the machine automatically increases its volt¬ 
age until it has double the voltage required to force the cur¬ 
rent against the resistance of one arc; in other words, until 
it is sufficient to force the current against the resistance of the 
the two arcs operating in series. Ordinarily this will be 
between 105 and 120 volts, varying with the amperage. See 
Page 400. 

To strike either arc alone it is only necessary to open the 
short circuiting switch of the lamp you are going to 
use, close the other short circuiting switch and strike the 
other arc in the usual way. Under this condition the dynamo 
will automatically generate only that voltage necessary to 
force the current across the resistance of the single arc. 

To extinguish either arc when both are burning, slowly 
feed the carbons of the lamp together until they are in 
contact, whereupon close the short circuiting switch of the 
lamp it is desired to extinguish. An arc may, of course, be 
extinguished merely by closing its short circuiting switch, but 
this would give the machine no chance to gradually decrease 
its voltage to meet the new condition. The bringing of the 
carbons of the lamp into contact with each other slowly, 
operates to lower the voltage of the generator gradually, 
so that there is no shock to it when the short circuiting 
switch is closed. 











MANAGERS AND PROJECTIONISTS 


471 


For directions as to the installation and care of the com- 
pensarc see general instructions, in addition to which full 
directions and wiring diagrams will accompany each set. 

The following data is supplied by the manufacturer. It 
will be found useful to those contemplating the purchase of 
a set. We do not vouch for the electrical data, though we 
have no reason to question its correctness. 



Figure 155. 

Steel Panel with Type AM Ammeter for Motor Generator Compensarc. 
Front Removed Showing Box Construction. 


WESTINGHOUSE MOTOR GENERATOR EQUIPMENT. 

—Westinghouse motor generator equipment for motion pic¬ 
ture theatres consists of a motor generator, with a single or 
polyphase A.C. motor, or a D.C. motor, generator, field 
rheostat, ballast rheostat, motor starter, and control 
panel. The motor generator is designed especially for 
this service, and is of sufficient capacity to deliver 
100 per cent, overload during the time one arc is 
projecting the picture and the carbons of the second 
lamp are warming up. The generators are compound wound 
for 75 volts at full load, and are designed to give approximate¬ 
ly the same voltage at 100 per cent, overload during the time 












472 


HANDBOOK OF PROJECTION FOR 


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"MANAGERS AND PROJECTIONISTS 


473 


the second arc is warming up. These equipments are built 
in various sizes suitable to meet the requirements of any the¬ 
atre from the smallest to the largest. 




BALLAST RHEOSTATS.— Ballast rheostats are an essen¬ 
tial part of the equipment, one being connected in series with 
each arc, as shown in Fig. 163. They serve as ballast to any 
fluctuations in current caused by variations in the resistance 
of the arc circuit. The rheostat consists principally of one 
frame of grids, a face plate with handle for varying the resis- 



Figure 157. 

Motor Generator With Polyphase A. C. Motor 












































474 


HANDBOOK OF PROJECTION FOR 


tance, two metal plates, one on each side, and wire mesh work 
guard over the top, back and bottom. The construction pro¬ 
vides for ample ventilation, and the enclosing feature allows 
their use in the projection room without fire risk. 



Figure 158. 

Motor Generator With Single Phase A. C. Motor 



Figure 159. 

Westinghouse Motor Generator With A. C. Motor 

THE CONTROL PANEL. —The control panel illustrated 
in Fig. 160 is made of black slate, 1x16x18 inches. The edges 
are beveled to add to appearance, and it is arranged for 
wall mounting on strap iron supports. The two sides, top and 
bottom, are enclosed by wire mesh, and the back by a steel 
plate. The panel is furnished complete with ammeter and 
shunt with 40-foot leads, voltmeter, and a mounting for the 





MANAGERS AND PROJECTIONISTS 


475 


generator field rheostat. The instruments have black faced 
dials and white pointers. 

The starters for the induction motors are either quick-make 
and break switches, Fig. 161, or type A auto starters, Fig. 162. 
Starting rheostats are furnished with the D. C.-D. C. motor 
generators. 

These equipments are designed to supply current for two 
arcs operating in independent parallel circuits, with a stabil¬ 
izing adjustable ballast rheostat in each circuit. This ar¬ 
rangement has a decided advantage in that each arc operates 
entirely independent of the other; hence, if one arc should 
“break” while being adjusted for the next reel, the other arc 



Figure 160. 

Control Panel. Front and Side Views. 

will be in no way affected. Furthermore, any fluctuations of 
current in one arc circuit are not accompanied by correspond¬ 
ing fluctuations of current in the other arc circuit. This 
arrangement also provides for simultaneously operating arcs 
of different current strength; for instance, an arc for a 
stereopticon requiring 25 amperes, and an arc for a spot light 
requiring 50 amperes. 

HEATING.— See General Instruction No. 10. 

INSTALLATION UNPACKING.— (See General Instruction 
No. 1). When uncrating the equipment, protect the various 
units against severe shocks and blows, especially if the tem¬ 
perature of the air be very low. Do not remove the blocking 
between the generator and motor frames until the set is 
finally installed at its permanent location. Furthermore, these 





476 


HANDBOOK OF PROJECTION FOR 


sets should never be moved from their permanent location 
unless suitable blocking is placed between frames of the 
motor and generator. This is necessary in order to prevent 
danger of bending the bearings out of alignment. Be sure 
to protect all the equipment from moisture (see General In¬ 
struction No. 1) and to make sure all windings of the motor 
and generator are dry before subjecting them to operating 
voltage. 

LOCATION. —All of the electrical equipment should be 
finally installed in a clean, dry, well ventilated place, and in 
such a manner as to be easily accessible for inspection and 

cleaning. The 
room or enclosure 
for the equip¬ 
ment should be 
sufficiently well 
ventilated so that 
the air tempera¬ 
ture will never be 
in excess of 104 
degrees Fahren¬ 
heit, See General 
Instruction No. 
10 . 

FOUNDATION. 

—I n order to 
make the motor 
generator readily 
accessible, it is 
advisable to con¬ 
struct a support- 
i n g foundation 
the magnetic hum 
and vibration being transmitted to the floor and the walls of 
the room. It is advisable to place on its top a vibration and 
sound-absorbing base, details of the whole being as 
follows: 

First, construct a sub-base of such height that when the 
whole thing is done the bottom of the bed plate of the 
machine will be about two feet above the level of the sup¬ 
porting floor. This supporting base is best made of cement, 
but may be made of brick, or even stone. It need not be 
solid, but only consist of an outer shell, 6 inches thick if it 
be of cement, or 8 inches if it be of brick. If the base is 



Figure 161. 

Quick Make and Break Switch 
which will raise it up, thereby preventing 




MANAGERS AND PROJECTIONISTS 


477 


built of brick, the mortar should be a rich lime mortar, 
strongly tempered with cement. 

Anchor bolts to hold down the top, or sound-absorbing 
base, should be built into the foundation, extending up far 
enough above the top of the sound-absorbing base so that 
nuts may be placed on the upper end, which should be about 
S l /2 inches above the top of the supporting foundation. These 
bolts must be so placed that they will not come in contact 
with the iron of the base plate. They are designed only to 
hold the sound-absorbing 
base down solidly on top 
of the supporting foun¬ 
dation. 

On top of the supporting 
foundation just described, 
a sound-absorbing base 
should be placed, consist¬ 
ing of two layers of solid 
planking, each layer two 
inches thick, and two lay¬ 
ers of solid cork, each 
layer two inches thick. 

Both layers of cork should 
be placed on the top of 
the supporting foundation, 
with the planking on top 
of the cork, the boards of 
one layer extending one 
way, and the boards of the 
other layer the other way. 

In other words, the two layers of planking should be laid 
at right angles, and the layers of the planking must be 
securely bolted or nailed together. 

After the cork and planking frame is in position, the 
anchor bolt nuts should be drawn up tight, remembering that 
they must not come in contact with the metal of the machine 
base plate. The motor generator may then be mounted on 
the plank frame and, if desired, the bed-plate may be bolted 
down to the plank frame by means of heavy lag screws, as 
holes are provided in the bedplate for this purpose. If so 
desired, heavy felt may be substituted for the cork, but cork 
is much more resilient, and will remain elastic indefinitely, 
whereas felt will not. 

When constructing the foundation and sound-absorbing 
base, it is essential that the top of the plank platform be 



Figure 162. 

Auto Starter 







478 


HANDBOOK OF PROJECTION FOR 


perfectly level, so that the oiling system of the motor- 
generator will not fail after the set is installed. 

NOMENCLATURE. —Where an installation is referred to 
in this article as a “two-light” machine, it is meant an equip¬ 
ment is designed to serve on a projection installation where 
the projectors are to be operated alternately for “change 
over” or continuous picture service. Such equipment may 
be used to warm up the carbons of the idle projector for a 
period of approximately one minute while the other projector 
is in operation. 

EQUIPMENT REQUIRED.— For each single-light instal¬ 
lation a motor generator and one ballast rheostat is required, 
the control switch being optional, whereas, for each two- 
light installation, a motor generator, two ballast rheostats 
and two control switches are necesary. 

INSTRUCTION FOREWORD.— For all cases wherein the 
instructions are equally applicable to both types of installa¬ 
tion, namely, two-light and single-light, no distinction will be 
necessary. However, when the instructions apply to only 
one of these types, then the type which is involved will be 
clearly indicated. 

A control switch is a single-pole, single-throw knife 
switch, which must be protected by a suitable cover if 
mounted on the frame of a motion picture projector. If the 
control switch is mounted on a switchboard panel, then the 
individual cover is not necessary. 

INSTALLATION OF MOTOR GENERATOR.— Install the 

motor generator in the projection room or, preferably, in a 
room located as near as possible to it. See General In¬ 
structions No. 1. 

MOTOR STARTING EQUIPMENT. —Install the motor 
control equipment for the motor generator as near to the 
motor generator as is convenient. 

BALLAST RHEOSTATS. —These should be installed either 
in the motor generator room or in the projection room. The 
ballast rheostat should be placed in an upright position, so as 
to allow free circulation of the air, vertically, between the 
grids. 

CONTROL SWITCHES. —The control switch for each bal-* 
last rheostat should, preferably, be mounted on the frame of 
the motion picture projector, with which the ballast rheostat 
is to be used, beside the projector table switch. 


MANAGERS AND PROJECTIONISTS 


479 


CONTROL PANEL— This panel should preferably be 
mounted between the two projectors, though any other con¬ 
venient place will do. 

WIRING AND CONNECTING. TYPE CS POLYPHASE 
MOTORS. —Connect the motor and auto-starter as per dia¬ 
gram furnished with the auto-starter. If the circuit is 2- 


641/ijf Rmoittr »/ 0*Umr Hhtttttr Ml 



Figure 163. 

Diagram of Wiring Connections for Two-Lamp Installation. 
(For one-lamp installation omit connections left of points A & B) 


phase, 4-wire, connect leads from one phase to motor termi¬ 
nals A1 and A2, and leads from other phase to terminals B1 
and B2. If circuit is a 2-phase, 3-wire, connect outside leads 
to terminals A1 and Bl, and middle lead to A2 and B2. If 
circuit is a 3-phase, connect any lead to any terminal. To 
obtain proper direction of rotation see instructions further 

























































ASO HANDBOOK OF PROJECTION FOR 

on. If fuses are used in the supply circuit, they should carry 
current in excess of current indicated in nameplate as follows: 

2-phase, 4-wire circuit, all leads, 25 per cent. 

2- phase, 3-wire circuit, outside leads, 25 per cent., middle 
lead, 75 per cent. 

3- phase, 3-wire circuit, all leads, 25 per cent. 

If circuit-breakers are used in the supply circuit, they 
should be adjusted to open the circuit in accordance with the 
above. 

Fuses in the starting circuit should carry four or five times 
the rated current. 

LUBRICATION. —Before starting, fill the oil reservoirs 
with the best quality of clean dynamo oil; overflow plugs 
must always be kept open. The old oil should be withdrawn 
occasionally, and fresh oil substituted. The old oil may be 
filtered and used again. See General Instruction No. 3. 

INSTRUCTIONS FOR OPERATING THE EQUIPMENT 
(TWO-LAMP INSTALLATION).—!. Before starting the 
motor-generator, see that all switches are open and that the 
ballast rheostat contact arms are on the right, indicated as 
button No. 7 in the diagram, Fig. 163. 

2. Close the motor starting switch. 

3. When motor generator reaches full speed, adjust the 
generator field rheostat until the voltmeter registers approxi¬ 
mately 75 volts. 

4. Close the cut-out switch on motion picture projector 
No. 1 and bring the carbons together. After the carbons 
have been warmed strike the arc by separating them slightly, 
and then close the single pole control switch, which short 
circuits part of the ballast resistance. 

5. Adjust the carbons, until the best possible operating 
condition is obtained. If the current is not of the correct 
value to give proper illumination of the screen, move the 
contact arm of the ballast rheostat to the left, one button at 
a time, until the proper illumination is obtained. The button 
which gives the proper illumination should be noted, so that 
it can be identified when projector No. 1 is again placed in 
operation. 

6. A short time before the end of reel No. 1, close the 
cut-out switch on projector No. 2 in order to warm up the 
carbons. 

7. After the carbons have been warmed, strike the arc and 
then close the single pole control switch, which short circuits 
part of the ballast resistance in ballast rheostat No. 2. 


MANAGERS AND PROJECTIONISTS 


481 


8. Adjust the carbons of No. 2 projector until the best pos¬ 
sible operating condition is obtained. If the current is not 
of a value to give the proper illumination, then move the 
contact arm of the ballast rheostat to the left, as explained 
in paragraph 5, until the desired result is obtained. 

9. At the proper time start projector No. 2 and immediately 
disconnect the circuit to No. 1 projector by opening the cut¬ 
out switch and the control (projector table) switch. 

10. Before shutting down the motor generator, disconnect 
the direct current end by opening all the cut-out and con¬ 
trol (projector table) switches, then open switch connecting 
motor to supply line. 

NOTE: The electrical equipment is fully as important as 
the projectors, and should receive equal care and attention. 

Read Instruction Book No. 5164A for information in detail 
on the installation and operation of Westinghouse motion 
picture motor generator equipment. It accompanies each 
set, or may be had, free of cost, by addressing the Westing- 
house Company, East Pittsburgh, Pa. 

REVERSING MOTOR GENERATOR.— The rotating ele¬ 
ment of the motor-generator should revolve in a clockwise 
direction, as observed by viewing the generator end of the 
set. If this is not the case when the motor is started, then 
the wiring connections for the motor must be changed. 

TO REVERSE MOTOR—TYPE CS POLYPHASE MOTOR. 

—To reverse a two-phase, 4-wire motor, the two leads of 
one phase should be interchanged. To reverse a 2-phase, 3- 
wire motor, the two outside leads should be interchanged. 
To reverse a 3-phase motor, any two leads should be inter ¬ 
changed. 

TO REVERSE TYPE AR SINGLE-PHASE MOTOR.- 

The direction of rotation is determined by the position of the 
brushes, and is indicated by a scale on the rocker ring, and 
a pointer on the front bearing bracket. The scale consists 
of three lines marked RR, N, and RL, respectively. When 
the rocker ring is turned so that the pointer is opposite RR, 
the motor will run in a right-hand, or clockwise, direction 
as you face the commutator, and when the pointer is opposite 
RL, the rotation will be left-hand or counter-clockwise. N 
is the neutral point; the armature will not turn if the pointer 
is opposite this line. To reverse the motor, therefore, loosen 
the rocker ring set-screw and turn the rocker ring until the 
pointer is opposite the line for the reverse direction of 
rotation. 


4 82 


HANDBOOK OF PROJECTION FOR 


CARE OF MOTOR GENERATOR. TYPE SK GENERA¬ 
TOR AND MOTOR. COMMUTATOR.— The commutator 
must be kept clean, and the brushes properly adjusted and 
fitted to the commutator. Wipe the commutator at frequent 
intervals, depending on the character of the service, with a 
piece of clean canvas cloth free from lint. Apply lubricant 
sparingly; a piece of paraffin rubbed lightly across the com¬ 
mutator surface will furnish sufficient lubrication. No other 
attention is required by a commutator which is taking on a 
polish and shows no sign of wear. A rough, raw, copper- 
colored surface should be smoothed with a piece of sand¬ 
paper, or fine sandstone ground to fit. In any case the final 
smoothing should be done with fine (No. 00) sandpaper. 
When using the paper or stone, lift the brushes and do not 
replace them until all grit is removed. NEVER USE 
EMERY PAPER ON THE COMMUTATOR. See General 
Instruction No. 7. 

BRUSHES. —The brushes are set in the neutral position at 
the factory, and the bracket to which they are attached is 
doweled in position. This adjustment should not be altered. 
It is correct for either direction of rotation. 

IMPORTANT.—New brushes should be of the same make 
and grade as those shipped with the machine. Brushes 
should have only sufficient clearance in the box to slide 
easily. 

RENEWING BRUSHES—TYPE AR SINGLE-PHASE 
MOTOR. —To remove brushes from the holder, turn the 
rocker ring so that the brushes are brought between the 
arms of the bearing bracket. Remove the screws of the clips 
that hold the brushes in place. After inserting new brushes, 
turn the rocker ring so that the pointer is opposite the line 
for the proper direction of rotation. The front bracket of 
the motor should not be removed if it can be avoided. If the 
bracket is removed, when replacing same, make sure the steel 
pin in brush-raising ring enters corresponding slot in the 
brushholder casting. Failure to observe this may result in 
poor operation. 

GENERAL POINTERS—GENERATOR EXCITATION.— 

When a generator is started it may fail to build up its volt¬ 
age properly. This may occur, even though the generator 
operated perfectly during the preceding run. This may be 
due to one or more of the following causes: 

(a) Slow speed. 


MANAGERS AND PROJECTIONISTS 


483 


(b) Open shunt-field circuit, caused by faulty connections 
or defective field coil or field rheostat. 

(c) Open armature or commutating-field circuit. 

(d) Incorrect setting of brushes. 

(e) Reversed series or shunt coils. 

(f) Poor brush contact due to dirty commutator or brushes 
sticking in holders. 

(g) Loss of residual magnetism. 

Examine all connections; try a temporarily increased 
pressure on the brushes; look for a broken or burned out coil 
in the rheostat. An open circuit in the field winding may 
sometimes be traced with the aid of a magneto and bell; but 
this is not an infallible test, as some magnetos will not ring 
through a circuit of such high resistance as some field wind¬ 
ings have, even though the winding be in good order and 
intact. If no open circuit is found in the rheostat, or in the 
field winding, the trouble is probably in the armature. But 
if it be found that nothing is wrong with the connections or 
the winding, it may be necessary to excite the field from 
another generator, or by some outside source. Calling the 
generator that we desire to excite No. 1, and the machine 
from which current is to be drawn No. 2, the following should 
be the procedure: 

Open all switches and remove all brushes from generator 
No. 1. Connect the positive brushholder of generator No. 1 
with the positive brushholder of generator No. 2; also con¬ 
nect the negative holders of the machines together. In 
making these connections it is advisable to complete the 
circuit through a switch protected by a fuse of about 5 
amperes capacity. Having completed the connection close 
the switch. If the shunt winding of generator No. 1 is all 
right, its field will show considerable magnetism. If possible, 
reduce the voltage of generator No. 2 before opening the 
exciting circuit; then break the connections. If this cannot 
be done, set the field rheostat contact arm of generator 
No. 1 on button marked “IN,” then open the switch very 
slowly, and gradually lengthen the arc which will be formed, 
until it breaks. 

A very simple means for getting a compound-wound 
machine to pick up, is to short-circuit it through a fuse 
having approximately the current capacity of the generator. 
If sufficient current to melt this fuse is not generated it is 
evident that there is something wrong with the armature— 
either a short circuit or an open circuit. If, however, the 
fuse has blown, make one more attempt to get the machine 


484 


HANDBOOK OF PROJECTION FOR 


to excite itself. If it does not pick up it is evident that 
something is wrong with the shunt winding or connections. 

If a new machine refuses to build up voltage, and the con¬ 
nections apparently are correct, reverse the field connections, 
i. e., interchange the field wires which are connected to the 
positive and negative terminals of the generator. If this 
interchange of connections does no good, re-establish the 
original connections and locate the fault as previously 
advised. 

BRUSHES. —See General Instruction No. 7. All brush 
faces resting on the commutator should be fitted to the com¬ 
mutator so that they make good contact over the entire area. 
This can be most easily accomplished after the brushholders 
have been adjusted and the brushes inserted. Lift one set of 
brushes so that they will not be forced against the com¬ 
mutator. Place a piece of No. sandpaper against the 
commutator with the sanded side toward the brushes. Re¬ 
place one brush in its holder and allow the spring to force 
it against the sandpaper. Draw the sandpaper in the 
direction of rotation under the brush, releasing the pressure 
as the paper is drawn back, being careful to keep the ends 
of the paper as close to the commutator surface as possible, 
thus avoid rounding the ends of the brush. After the first 
brush is properly ground, it should be lifted sufficiently to 
prevent its being forced against the commutator, after which 
the remaining brushes of the set may be similarly ground, 
one at a time. 

By this means a satisfactory contact is quickly secured, 
each set of brushes being similarly treated in turn. If the 
brushes are copper plated, their edges should be slightly 
beveled, so that the copper does not come in contact with the 
commutator. 

INSPECTION. —Make frequent inspection to see that (a) 
brushes are not sticking in holders; (b) pig-tail shunts are 
properly attached to brushes and holders; (c) tension is 
readjusted as the brush wears; (d) copper plating is cut back 
so it does not make contact with commutator; (e) wornout 
brushes are replaced before they reach their wearing limit 
and break contact with the commutator; (f) any free copper 
picked up by the face of the brushes is removed. 

COMMUTATOR. —See General Instruction No. 7. 

HEATING FIELD COILS.— Heating of field coils may re¬ 
sult from any of the following causes: (a) too low speed; 


MANAGERS AND PROJECTIONISTS 


485 


(b) too high voltage; (c) too great forward or backward lead 
of brushes; (d) partial short-circuit of one coil; (e) overload. 

HEATING OF ARMATURE. —Heating of armature may 
result from any of the following causes: (a) too great a load; 
(b) a partial short-circuit of two coils, heating the two par¬ 
ticular coils affected; (c) short-circuits or grounds in arma¬ 
ture winding or commutator; (d) bad commutator, with 
consequent large circulating current in armature coils under¬ 
going commutation. 

HEATING OF COMMUTATOR.— Heating of commutator 
may result from any of the following causes: (a) overload; 

(b) sparking; (c) too high pressure. 

BUCKING. —“Bucking” is the very expresive term de¬ 
scriptive of the arcing between adjacent brush arms. In 
general, bucking is caused by excessive voltage between com¬ 
mutator bars, or by abnormally low surface resistance on the 
commutator between brushholders of opposite polarity. Any 
condition tending to produce poor commutation, increases the 
danger of bucking. Among other causes are the following: 
(a) rough or dirty commutator; (b) a drop of water on the 
commutator from the roof, leaky steam pipes or other source; 

(c) short-circuits on the line producing excessive overloads. 

HALLBERG D. C. TO D. C. MOTOR GENERATOR.— The 

Hallberg D. C. to D. C. motor generator consists of a D. C. 
motor, directly connected to a specially wound generator 
which delivers current to the arc at arc voltage, so that there 
is no necessity for resistance in series with the arc. The 
only waste is the power consumed in the machine itself. The 
saving accompanied by its installation will therefore be the 
difference between its efficiency and the efficiency of rheo¬ 
static resistance, plus the interest on the sum the motor 
generator costs over and above the cost of a rheostat or 
rheostats. 

The manufacturer gives the following data. We cannot 
vouch for the efficiency claims, which, even though we con¬ 
cede their entire correctness, can only be maintained if the 
machine be kept in first-class condition. 


Line fuses 

LINE 

INPUT. 

Line watts. 

required. 

Line volts. 

Amperes. 

20 Amp. 

110 

17 

1,870 

10 Amp. 

220 

10 

2,200 

5 Amp. 

550 

4 

2,200 


486 


HANDBOOK OF PROJECTION FOR 


Arc 

voltage. 

50-55 

50-55 

50-55 


OUTPUT AT ARC. 


Are 


amperes. 

Arc watts. 

Watts loss. 

Efficiency. 

30 

1,650 

220 

88% 

30-35 

1,650 

550 

75% 

30-35 

1,650 

550 

75% 


In considering a matter of this kind it should be remem¬ 
bered that when opposed to 110 volts a rheostat is less than 
50 per cent, efficient. In other words even where the supply 
voltage is only 110 there is more power consumed in the 
rheostat than is used in the arc itself. If the supply voltage 



be 220, then the power consumed in the rheostat is about 
three times the power consumed in the arc. 

Fig. 164 shows the general make-up of the 110 volt type of 
D. C. to D. C. motor generator. While constructed along the 
lines of a motor generator, this machine is, in the strict sense 
of the word, only in part a motor generator. The principle 
involved permits the use of a smaller and more efficient motor 
and generator than would be possible were the apparatus a 
straight motor generator set. 

The 110 volt outfit is provided with an automatic starting 
box and light controller by means of which the projectionist 
may vary the arc amperage anywhere between 20 to 30 on 
the 25 ampere size; from 30 to 40 on the 35 ampere size; and 















































MANAGERS AND PROJECTIONISTS 


487 


from 40 to 60 on the 50 ampere size. By the use of a special 
controller (furnished upon request) it is possible to cause 
all D. C. to D. C. sets to deliver less than their rated minimum 
amperage, although we believe that if this is done there will 
be some sacrifice in efficiency. 

Fig. 165 shows the Hallberg D. C. to D. C. straight motor 
generator set, made for supply voltage ranging from 200 to 
750, in which the generator is designed and wound to deliver 
a constant amperage to the arc, without the use of resistance 
in series therewith. These sets are supplied with a complete 
automatic starter and light controller; also they have a pulley 
coupling between the motor and generator, on which it is 
possible to 
place a belt for 
driving the 
motor gener¬ 
ator by means 
of an engine. 

Under this 
condition the 
generator e n d 
will supply a 
projection arc, 
and if desired 
the motor end 
can be made 
o supply a 
limited number 
of lights or fan 

motors. This latter is a feature which might, under some 
conditions, be of considerable value to the exhibitor. 

Another advantage in connection with this set is that its 
low voltage side is an entirely separate unit, which may be 
run as an ordinary dynamo by an engine of from three to 
six horse power. Operated in this way it may be made to 
supply a projection arc. The other half, which is merely an 
ordinary D. C. motor, may be removed from its base and 
used as a regular motor for any purpose desired. 

We do not find it practical to give wiring diagrams for this 
class of apparatus, because the diagrams vary for different 
voltages and these sets are usually built to specification to 
suit the purchaser. We would therefore recommend that* the 
wiring diagrams which accompany the set be carefully put 
away and kept for future reference. 



Figure 165. 



488 


HANDBOOK OF PROJECTION FOR 


The Hallberg D. C. to D. C. motor generator is also made 
in a new, more modern design, illustrated in Fig. 166. This 
machine has only two bearings, both of which are ball bear¬ 
ings. The various machines have outputs ranging from 25 to 
150 amperes. With this type of motor generator the manu¬ 
facturer will furnish controller panels, including the necessary 
voltmeters, and ammeters for double arc operation where the 
generator capacity is 70 amperes or more. 

INSTRUCTION NO. 1. INSTALLATION.— (See General 
Instruction Nos. 1 and 2.) 

INSTRUCTION NO. 2. CONNECTIONS.— All electrical 

connections should be made as shown in the wiring diagram 
accompanying each machine, and they must be clean and 
tight. Fuses should not have a higher capacity than that 
indicated by the diagram. 

INSTRUCTION NO. 3. BRUSH TENSION.— After the 
machine has been properly set and connected, rotate the 

armature by hand and 
examine each carbon 
brush to make sure that 
it moves freely, without 
the slightest friction, in 
the brushholder. Make 
sure that the flexible 
copper cable, or pig¬ 
tail as it is called, is 
properly clamped b y 
the screw in the brush- 
holder casting. When 
the brush moves freely 
in the holder, the next 
thing to receive attention is the tension spring which holds 
the brush against the commutator. See General Instruction 
No. 8. The pressure exerted by the brush tension spring 
may be varied by changing the end of it to different notches 
provided in the brushholder casting. Any required degree of 
tension can be had by using the different notches. 

INSTRUCTION NO. 4. OILING.— The oil chambers should 
contain enough oil to give the rings (see Fig. 148) a good dip. 
The oil level may be seen in the gauge on the sides of the 
bearings. It should be at the top of the gauge. When 
starting the machine, lift oil chamber covers and see that 
the oil rings are turning freely and carrying oil to the shaft. 



Figure 166, 



MANAGERS AND PROJECTIONISTS 


489 


The old oil should be drawn off every month or two. This 
is done by unscrewing the drainage plug at bottom of the 
bearing. After draining off the oil replace it with new. See 
General Instruction No. 3. 

SPECIAL INSTRUCTION FOR BALL BEARINGS.— The 

latest type D. C. to D. C. motor generator, Fig. 166, is equipped 
with ball bearings. See Instruction No. 7. for Hallberg’s 
Twentieth Century Motor Generator Set. For removing ball 
bearings see Instruction No. 8 under the same heading, the 
ball bearings of the two machines being of the same type. 

INSTRUCTION NO. 5. SETTING OF BRUSHES.— Ma¬ 
chines are shipped from the factory with the brushholders 
and brushes properly set. The position of the brushes is 
approximately half way between the poles. In the motor, they 
are placed one or two segments back (that is, against the 
direction of rotation) of the exact middle or neutral point, 
while in the generator they are set one or two segments 
forward. The brushholders should be placed on the studs in 
such position that the brushes in different .holders will not run 
in the same line on the commutator. This will help to avoid 
grooving. 

INSTRUCTION NO. 6. STARTING SET.— First see that 
the starting box lever has moved to the off position. If there 
is a regulating rheostat on the motor end, its handle should 
be moved as far as possible in a contra clockwise direction. 
If there is one on the generator end its handle should be 
moved as far as possible in a contra clockwise direction. 
Close the main switch and move the lever of the starting box 
over the contacts, leaving each one for about one second, 
until it is against the magnet, which will hold it. If the set 
has not started when the fourth contact point is reached, 
immediately open the main switch and ascertain the trouble. 
When the set is running the current may be adjusted by 
means of the regulating rheostats. 

9 INSTRUCTION NO. 7. STOPPING SET.— Open the main 
switch and let the starting box operate itself. The lever will 
be released when the motor has slowed down, when it will, 
or should, fly back to the “off” position. If the contacts 
become rough and prevent the lever from moving all the way 
back, they should be smoothed up with No. 0 or 00 sandpaper. 
The lever must never be fastened or allowed to stick at an 
intermediate point. 

INSTRUCTION NO. 8. CARE OF BRUSHES AND COM¬ 
MUTATOR.— (See General Instruction No. 8.) 


490 


HANDBOOK OF PROJECTION FOR 


HALLBERG’S TWENTIETH CENTURY MOTOR GENE¬ 
RATOR SET.— J. H. Hallberg, New York, puts out a motor 
generator set, known as the “Twentieth Century Motor 
Generator,” shown in Fig. 167. The machine occupies a floor 
space 15 by 31 inches, and is 15 inches in height. Its weight 
is a little less than 500 pounds in the 70 ampere size, the 40 
and 130 ampere machines being respectively less and greater 
in weight. The machine is compact, rigid in construction, 
and its parts are easily accessible for adjustment or repair, 
as may be seen by an examination of the various plates. 

The machine is made in capacities of 20-40 amperes, 30-70 
amperes, and 60-130 amperes. The 30-70 ampere size is the 



Plate 1, Figure 167, 


capacity more largely in demand for moving picture work, in 
that it will operate with a fair degree of efficiency on a 34) 
ampere load, and will carry two 50 ampere arcs for the short 
period of time necessary to make a change from one pro¬ 
jector to the other. It must not be understood from this 
that the generator should be allowed to carry a 100-ampere 
load for more than one to one and a half minutes. 

The machine delivers direct current to the arc, at arc 
voltage, without any resistance interposed in the circuit, 
which means, of course, that it is a specially compounded 
generator, and, to go a little further, a specially compounded 








MANAGERS AND PROJECTIONISTS 


491 


generator pulled by an A. C. motor, the two armatures being 
mounted on one shaft, and contained in one housing, with a 
ball bearing at either end of the shaft. 

Plate 1 supplies a view of the whole machine, with the 
various parts numbered. 

NO. 1.—LUBRICATION. —The lubrication of this machine 
differs from that of most other motor generator sets used for 
moving picture work, in that grease is used instead of oil. 

The grease chambers may be filled in two ways: First, if 
you have purchased your grease in a “gun,” or if you have 
a “gun” which can be filled with grease, having removed 
screw, 23, Plate 1, and a similar one on the opposite diameter 
of the grease chamber cover, you can place the spout of 
the gun in the upper hole and force grease in. This will 
force the old grease out at the lower hole, and the job will 
be a fairly complete one. This operation must be performed 
for the grease chamber at each end of the armature shaft 
When through you will, of course, replace the screws. 

Another way is, if you have no grease gun, to remove 
screws 24 (four of them) on the end of the cast iron cap 
which covers the grease chamber. You can then pull the 
cap off, clean out the old grease, and pack the chamber with 
fresh lubricant. It would be well to wash out the grease 
chamber thoroughly with kerosene or gasoline after the old 
grease is removed. 

Still a third way is to remove screw, No. 23, Plate 1, and 
insert in lieu thereof a compression grease cup having a stem 
of the same diameter and thread as a J^-inch gas pipe. 
Where the compression grease cup is used when it is desired 
to force grease in it will be necessary first to remove the 
screw in the opposite diameter to screw 23, Plate 1, same 
being immediately below the grease cup, in order to allow 
an equal amount of old grease to flow out. Where the com¬ 
pression grease cup is used it is merely designed that the 
cup take the place of a grease gun—therefore it should be 
a large one and only used to force a large quantity of grease 
in about once every 60 to 90 days, it being expected that 
when the run is, say, twelve to fourteen hours per day one 
greasing will last for that length of time. 

CAUTION.—Don’t use any and every kind of grease. The 

grease serves ball bearings, and if it contain alkalis or acids 
you may expect trouble and plenty of it. For this reason our 
advice is : Use only grease procured from the manufacturer 
of the machine. You may regret it if you do otherwise. 


492 


HANDBOOK OF PROJECTION FOR 


NO. 2.—LOCATING THE MOTOR GENERATOR.— (See 
General Instruction No. 1.) 

NO. 3.— INSTALLATION.— (See General Instruction No. 2.) 

NO. 4 .— CLEANLINESS.— (See General Instruction No. 4.) 

NO. 5.—LOOSE CONNECTIONS.— (See General Instruc¬ 
tion No. 6.) 

NO. 6.—AMMETER AND VOLTMETER.— (See General 
Instruction No. 7.) 

NO. 7.—REMOVING END BEARING BRACKET 2, P. 1.— 

It will never be necessary to remove this bracket unless some 
fault should develop through the use of improper grease, or 
a very improbable inherent imperfection in the ball bearings, 
but should such a thing occur you may remove end bearing 
bracket 2, P. 1, by first removing four hexagon shaped nuts, 
holding the cast iron cover of the grease chamber. These nuts 
do not show in the plates, but correspond to nuts 24, P. 1, in 
the grease chamber cover at the opposite end of the machine. 
The studs, which are held by four hexagon nuts, not only 
hold the outside cast iron cover to the grease chamber, but 
extend through and into an inside cast iron grease chamber 
cover. The ball bearings are clamped between these two 
end covers, and these bearings should never be removed 
from the armature shaft except it be desired to install a new 
bearing. Therefore, after having removed the hexagon nuts 
and the outside cover, using a copper punch and hammer, 
gently drive the studs inward to loosen the inside cover. 
Having done this, remove bolts 4, P. 1 (four of them), where¬ 
upon you may pull away end bearing bracket 2, P. 1. 

NO. 8.—TO REMOVE THE BALL BEARING at the A. C. 
end of the armature, follow Instruction No. 7. Having done 
so you will see on the end of the shaft a nut having in its 
edge a saw kerf, and in its face the head of a machine screw. 
This screw acts as a lock nut by compressing the edges of 
the nut where the saw kerf is made, thus locking the threads 
to the shaft. Loosen it and remove the nut, which has a 
right-hand thread. This will release the ball bearing, which 
may be pulled out. When installing the new ball bearing 
or replacing the old one, be sure and get it on the shaft 
straight or “square.” If you attempt to put it on a slant it 
won’t go, but if started on just right will slip on easily. 
Having it in place, set up the lock nut as tight as you can 
get it, and then set up the screw in its face, thus locking the 
nut to the shaft. In replacing end bearing bracket 2, P. 1, 
proceed carefully, and don’t try to force it on over the ball 


MANAGERS AND PROJECTIONISTS 


493 


bearing. When you get it exactly right it will slip on with¬ 
out any trouble whatever. If it does not do so, that is your 
fault and not the fault of the bracket—you have not placed 
it exactly in the right position with relation to the bearing. 
If you try to force it on you will probably succeed in ruining 
the ball bearing. The rest of the process of replacing is 
simply the reversal of the process of disassembling. 

NO. 9.—TO REMOVE THE ARMATURE lift out all the 
brushes, 17, P. 2. To do this lift finger 9, P. 3, and pull the 
brush out, letting it hang by its pig tail so that you will be 
sure to get it back in the right holder. Next remove bolts 
4, P. 1 (four of them). Next remove the four hexagon¬ 
headed bolts, 24, P. 1, holding grease cover cap, 22, P. 1, and 


H3 

o 

•o 

o 


Q 

C 

n- 


pull the armature, carrying end bracket, 2, P. 1, with it, 
straight out at the A. C. end. 

CAUTION.—Never lay an armature down flat on anything. 

Either stand it on end, or else support it on two chairs or 
boxes, using the ends of its shaft for the purpose. If you 
lay the armature itself down on the floor or table you are 
likely to injure the insulation. The replacement of the arma¬ 
ture is simply a reversal of the process of taking it out, 
doing each step in its turn. 

NO. 10.—TO REMOVE THE COMMUTATOR END 
BEARING BRACKET, 3, P. 1, first remove four hexagon¬ 
headed bolts 24, P. 1, in grease cover cap, 22, P. 1. Next lift 
out all the brushes. They may be lifted out by raising finger 
































































494 


HANDBOOK OF PROJECTION FOR 


9, P. 3. Let them hang by their pig tails, so that you will get 
them back in the right holder. Remove bolts, 4, P. 1 (four of 
them), whereupon the bracket may be pulled away. 

CAUTION. —The four hexagon-headed bolts extend through 
and hold the plate covering the inside end of the grease 
chamber. This cover will sometimes stick slightly. Before 
removing the bolts, but after having backed them out for 
three or four turns, tap on them lightly with a hammer, in 
order to loosen the inside grease chamber cover. 

NO. 11.—TO REMOVE BRUSH YOKE, 6, P. 2, follow In¬ 
struction No. 10, then loosen screw, 7, P. 2, whereupon you 
may pull away 'the yoke, carrying all the brushholders. 

NO. 12.—BRUSHHOLDER STUD.— Should it ever be neces¬ 
sary to remove brushholder stud, 8, P. 2, it may be done 
by loosening nut, 10, P. 2, but if you do this, be very careful 
in reassembling that the insulation, which consists of two 
mica washers, 9, P. 2, and a mica sleeve around the bolt, be 
not in any way injured. If this insulation is not perfect, then 
the whole frame of the machine will be charged with 
potential. In loosening these parts it will be well to remove 
nut 10, P. 2, and thoroughly clean the contact between it and 
the copper clip to which the wire is connected. In reassem¬ 
bling be sure to set up nut 10, tight, else you will not have 
good electrical contact; also it is essential that the lock nut 
behind nut 10, which holds the insulation in place, be set up 
tight, else the brushholder stud will vibrate and thus cause 
trouble. 

NO. 13.—BRUSHHOLDER, 12, P. 2, may be slipped off at 
any time by loosening screw 16, P. 2. Before taking off the 
brushholder you should make a scratch mark at its end on 
the stud, so that in reassembling you may get it back in 
exactly the same position it formerly occupied. 

NO. 14.—CARE OF THE COMMUTATOR.— (See General 
Instruction No. 8.) 

NO. 15.—TO INSTALL NEW BRUSHES.— First raise 
finger 16, P. 1 (shown better at 9, P. 3), and remove the 
screw holding the end of the pig tail to the brass casting, 
then lift out the brush, put in the new one and attach its pig 
tail to the casting the same as the old one was. The face of 
the new brush must be ground to fit to the curve of the com¬ 
mutator. To do this lift out all the brushes you are not 
replacing, then place on the commutator, sand side out, a 
strip of No. y 2 sandpaper long enough to extend one and one- 
half times around its circumference. Lower the new brush 


MANAGERS AND PROJECTIONISTS 


495 


on this sandpaper under the pressure of its tension spring, 
and revolve the armature by hand, or by pulling a long piece 
of heavy cord bound around the commutator one or two 
times, until the brush is ground down to a proper bearing. 
It is also possible to lay a piece of sandpaper on the com¬ 
mutator and pull it back and forth, but the other way is the 
better. Do not apply power to the motor for grinding 
brushes. 

NO. 16.—HEATING. —(See General Instruction No. 11. ) 

NO. 17.—GENERAL REMARKS.— Plate 3 shows the con¬ 
struction of the brushholder in detail, 14 being the pig tail, 
11 the spring which 
governs the amount 
of tension supplied 
the brushes through 
finger 9, P. 3. Plate 
4 shows the pole 
piece construction, 
main poles A-A be¬ 
ing wound and B-B 
not wound. In like 
manner interpoles or 
“commutating poles” 

C-C are wound, while 
D-D shows the core 
of the poles without 
the windings. The 
machine is entirely 
self-contained, and 
requires no special 
base. It may either 
be set on a cement 
floor and bo lted 
down or on any other 

reasonably solid ., 

foundation, but if installed in the projection room it should 
be set on a small rubber pad or heels of good live rubber. 
This will take up all vibration, make the machine practically 
noiseless, and there will be no necessity for bolting it down 

at all. . 

The efficiency of the machine is claimed by the manufac- 
turer to be between 65 and 70 per cent., depending upon 
local conditions and the degree of intelligent care given. 

The accompanying connection diagrams are quite plain, 








496 


HANDBOOK OF PROJECTION FOR 


and may, I believe, be followed without any trouble by the 
average well-posted projectionist. Plate 5 shows the various 
connections for single, two and three phase 110 or 220 volt 
circuits. 

All Hallberg Twentieth Century A. C. to D. C. motor 
generators are so wound that they may be used either for 110 
or 220 volt current, merely by changing the connections as 
shown in P. 5. 



TWO-ARC MACHINE. —P. 6 shows the wiring of the D. C. 
end, with two projection arcs connected in multiple with 
each other. By this arrangement arc No. 1 may be operated 
at any desired amperage between 30 and 60 by moving the 

handle of the field 
controller. When it 
is desired to start the 
second arc and fade 
the first picture into 
the next, the operating 
or machine switch on 
machine No. 2 may 
be closed, and when 
the time comes to 
swing over to that 
machine its arc is 
started merely by 
bringing the carbons 
together and separat¬ 
ing them in the usual 
manner, which will 
automatically extin¬ 
guish the arc of ma¬ 
chine No. 1, thus 
fading one picture into 
the next. This is a 
matter which will 
require some practice, but once it is mastered it is quite 
possible to secure fair results. But where this plan is 
used the projectionist will do well to burn craters on his 
carbons when there is no picture on the screen. In other 
words, he should have a supply of burned-in carbons. It 
will probably also be found necessary to recenter the upper 
crater by raising the lamp about one-quarter of an inch 
before starting the arc. 

The projector motor must, of course, be started just before 


Plate 4, Figure 170. 



MANAGERS AND PROJECTIONISTS 


49? 


the arcs are changed over. The manufacturer claims that 
one of the peculiarities of this generator is that it picks up 
and steadies its arc almost instantly. 

P. 7 shows the generator with its control panel (Panel Z) 
connections arranged for single and double arc operation. 
When the handle of the switch is down, the connections give 
the same results as those of P. 6, but ammeters and volt¬ 
meters are added, so that the current may be adjusted by the 
field rheostat to any desired value within the limits of gener- 


tS'rsSlt 





Siftcir PfAsr 
pro Huts 




TMft PMS4S 
2ZO+4TS 



::: 





Plate 5, Figure 171. 


ating capacity. In this position the compound winding con¬ 
nected to Cl and C2, opposes the shunt field, which causes the 
generator to produce constant current for the operation of 
one arc at a time, in which case no resistance is necessary in 
series with the arc, the generator having within itself the 
necessary flexibility to properly control the arc. 

By comparing the front and side views of the panel, it 
will be seen that Cl and C2 represent the hinge clips of the 
switch, and are therefore common to both its down and up 
positions. In the down position one switch blade connects 


















































498 


HANDBOOK OF PROJECTION FOR 


C2, LI and L2, and the second blade Cl and A+. Let us 
assume that lamp 1 is burning, then the flow of current 
starting with A+ at the generator to A+ of the panel, from 
there to Cl through the switch blade, thence to Cl of the 
generator through the series field back to C2, thence to LI 
through the other switch blade, to the projector switch con¬ 
trolling the arc, back from the arc through the negative con¬ 
nection, thence to LI L2 of the ammeter shunt, to A— of 

the shunt, the arma¬ 
ture terminal of the 
generator, and after 
passing through the 
armature it again 
flows out of A+ and 
the process repeats 
itself. The circuit 
would have been the 
same if we had as¬ 
sumed lamp 2 burn¬ 
ing, instead of lamp 1, 
except that the cur¬ 
rent would have 
passed from C2 to L2, 
instead of LI. 

The shunt field 
terminals F, F, re¬ 
spectively, are con¬ 
nected to one arma¬ 
ture terminal at the 
machine, A— r and to 
the other through the 
field rheostat on the 
panel to A+. When 
it is desired to oper¬ 
ate the two arcs at 
one time, the switch handle must be thrown to the up position, 
which connects in each arc circuit the necessary ballast 
resistance, reverses the current through the series field, so that 
the series and shunt fields assist each other and short circuits 
the terminals of the rheostat, these last two connections result¬ 
ing in the generator producing maximum voltage. 

With two arcs burning there is a voltage drop of 5 to 6 
volts in each resistance, and under certain conditions, as 
when large fluctuations of-line voltage occur, it may be found 
desirable to operate the arcs with the switch in this position, 





























MANAGERS AND PROJECTIONISTS 


499 


even when only one arc is burning. The highest efficiency, 
however, is obtained with the switch in the one-lamp posi¬ 
tion, and the two-lamp position is only intended to allow for 
more perfect dissolving when changing from one projector 
to another. 

The flow of current for the two lamp position of the switch, 
considering first, lamp 1 as burning, would be from the posi¬ 
tive armature terminal A+ to A+ on the panel board, which 
by a cross connection brings the current to the top left hand 
terminal, thence through the switch blade to C2, thence to 
C2 the series field terminal at the generator, through the 

z 

VIEW 3/e* V/KtV 



series field to terminal Cl, thence to Cl on the panel, through 
the switch blade to top right hand switch, thence to common 
ending of ballast coils, through top ballast coil to LI, thence 
to positive side of lamp 1 projector switch, through the arc 
back through the negative side of projector switch, thence to 
LI L2 of ammeter shunt to A—, thence to negative armature 
terminal A—, through the armature and out again at A-f, after 
which the flow of current continues as before. The reversal 
of current through the series field is accomplished by the 









































500 


HANDBOOK OF PROJECTION FOR 


cross connection of A+ on the panel, and the left hand top 
switch blade short circuits the rheostat terminals F and A+, 
cross connected terminal. 

If lamp 2 is also burning then current will also go through 
the bottom resistance coil to L2, thence to lamp 2 and back 
through the negative connection to LI L2 of the ammeter 
shunt, and back to the generator as before. In some panels 
the ammeter shunt is mounted on the terminals of the am¬ 
meter, so that LI L2 becomes one of the ammeter terminals. 

HALLBERG SERIES ARC MOTOR GENERATOR.— 
Within the past few years there has been developed and put 
into service a modified form of the old series D. C. Arc 
dynamo, the generator automatically adjusting itself to de¬ 
liver from 40 to 60 volts to each one of the arcs. With this 
system, when all lamps are off, their terminals short cir¬ 
cuited with a switch, and the generator operating, when one 
short circuiting switch is opened (carbons of that lamp being 
in contact) and the carbons are separated, the arc will be 
struck and the generator will automatically supply the re¬ 
quired number of volts for maintaining the arc, regardless of 
the carbon separation or arc resistance, within reasonable 
limits, of course. A second lamp may be similarly switched 
on, whereupon the generator instantly and automatically sup¬ 
plies exactly the additional voltage required for the added 
resistance of the second lamp. 

For motion picture projection, where not more than two 
arcs are required at one time, it is possible to use this scheme 
without introducing any movable regulating device?, and it 
is not necessary to shift the brushes, because by properly 
designing the magnetic circuit and by a proper arrangement 
of the shunt and series field it is possible to give practically 
constant current from such special generator, regardless of 
whether one or two arcs are burning. 

The Hallberg Series Motor Generator, illustrated in Fig. 
174, is of this type. It is of the horizontal type, meaning by 
this that its armature shaft is in horizontal position. The 
A. C. armature, or rotor, and the D. C. armature are mounted 
on one short, heavy shaft, which is supported at either end 
by two large double-row, self-aligning ball bearings. Unlike 
the Hallberg motor generators hereinbefore described the 
A. C. motor frame is made in a separate unit, which is bolted 
to a bored and faced-surface on the generator field frame. 
This construction is, when assembled, to all intents and pur¬ 
poses one solid frame, but with the advantage that it is very 
easy to separate the A. C. end from the D. C.; also it per- 


MANAGERS AND PROJECTIONISTS 


501 


mits of very efficient ventilation, and decreases the weight 
of material required for a unit of given output. 

The machine may be had for 25, 33, 40, 50 and 60 cycles, and 
either for single, two or three phases in the same frame. 
The machine is now standardized, and obtainable in the fol¬ 
lowing sizes, viz.: double 50 ampere, which is adjustable from 
40 to 60 amperes; double 75 ampere, adjustable from 60 to 
85 amperes; and double 120 amperes, adjustable from 75 to 
135 amperes, all three types operating either one arc or two 
arcs in series. 

With this type the wiring is simple, there being required 
one loop from one terminal of the generator through the first 
projector switch, then through the second projector switch. 


and through a 
third, if it is a 
three- projector 
installation, the 
switch of the last 
projector being 
connected to the 
other terminal of 
the generator. 



The diagram, 
Fig. 175, illus¬ 
trates the very 
simple connec¬ 
tions between the 
motor generator, 


Figure 174. 


the instrument panel, and the projector table switches, it 
being understood that if three projectors are installed, it merely 
means extending the loop of the circuit to include an additional 
projector table switch. 

The over-all dimensions of the Hallberg Series Arc Motor 
Generator referred to is thirty inches in length, by about 
twenty-two inches diameter for the largest size. The weight 
varies from 450 to 650 pounds, depending upon the capacity 
of the set, and the phase for which the machine is made, the 
heaviest being the 120 ampere capacity machine, wound for 
25 cycles, single phase current. 

Some theatre managers insist upon complete duplicate 
motor generator installation. For such a demand the Hall¬ 
berg motor generator is made with different winding, so as 
to provide the maximum number of amperes required for 
the operation of one arc only, and then two motor generators 
are installed as per Fig. 176, connected to a set of transfer 


502 


HANDBOOK OF PROJECTION FOR 


switches and bus-bars, with one instrument panel and a field 
rheostat for each generator. This installation is so arranged 
that either one of the generators may operate either one of 
the two arcs merely by operating two switches, or both gen¬ 
erators may be made to supply double the current to either 
one of the arcs. 

The instructions for the setting, care and operating of the 
Series Arc Motor Generators are in every way the same as 
those given for the Hallberg Twentieth Century Motor Gen¬ 
erator sets, page 490, with the single exception of instruc- 


’H' 

RrtNEL. 

V/£\sv 



tion No. 9, Page 493, which for the Series Arc machine 
should be as follows: 

TO REMOVE ARMATURE. —First make certain that all 
electrical connections are broken, so that no parts will be 
carrying current. If the connections between the set and 
the line are broken at the set before the disconnections are 
made, the ends that will be separated should all be marked 
so that when the connections are re-established they will be 
correctly made. However, coiled motor leads of 20 inches or 
more length will obviate the necessity of doing this, or open¬ 
ing the main switch will suffice if the complete set need not 
be moved from its position in order to make the armature 
accessible. 



























MANAGERS AND PROJECTIONISTS 


503 


The next thing is to lift the brushes on the generator side 
out of the brush holder boxes, care being taken that in this 
process the position of the brush rocker is not changed. It 
is also necessary to mark the side of the brushes which is 
towards the direction of rotation, so that when the brushes 
are put back in their respective holders they will be put in 
with the same side forward. This will insure good contact 
when the set is reassembled. 

Next, remove the cap screws and the outside ball bearing 
caps on both the motor and generator ends. Then remove 
the cap screws which hold the bearing bracket to the motor 
frame on the alternating current side, and then remove the 
bracket complete. This can be done without taking the ball 



bearing off the rotor shaft. Next remove the cap screws 
which fasten the motor frame to the generator frame, and 
then completely remove the motor frame. 

After this has been done the armature can be slid out of 
the Generator. Care, however, must be taken in doing this, 
so that the direct current armature winding will not be 
scratched or in any other way damaged. The armature 
being out of the machine, in order to remove the ball bear¬ 
ings and inside caps so that they can be employed on a new 
armature, which it is assumed is to be installed, the follow¬ 
ing procedure should be followed. Loosen the small screw 
in the split portion of the ball bearing clamp nuts, and then 
turn the ball bearing clamp nut to the left, using a hammer 
and blunt cfiisel, placing the chisel against the lugs of the 
clamp nuts. When the clamp nuts have been removed tne 




























































504 


HANDBOOK OF PROJECTION FOR 


ball bearings are to be pried off the shaft, and after that the 
inside ball bearing caps can be removed. 

The middle fan of this set is made in two halves. To 
remove it it is necessary to loosen a screw on one side of 
the split casting, then remove the screws which hold the 
castings to the shaft itself. The fan can be opened like a 
hinge, removed and made available for mounting in exactly 
the same manner on the shaft of the new armature. 

In re-assembling the set the reverse of the process de¬ 
scribed should be carried out. The first thing to do is to 
place the inside ball bearing caps on the new armature 
shaft, first determining by the conditions of the felts in the 
grooves of the caps whether or not new felts should be in¬ 
serted. The ball bearings are then placed on the shoulders 
on the shaft provided for that purpose. The clamp nuts are 
to lock the ball bearings in position, and the importance of 
putting those clamp nuts on very tightly must be emphasized. 
It cannot be satisfactorily done by turning the clamp nuts in 
position with a wrench. It must be done with a blunt cold 
chisel and a hammer. The hammer blows should be heavy, 
so that the nut will be positively locked hard up against the 
ball bearing race. The clamp nuts are made of malleable 
iron and will not crack. After the lock nuts are driven on 
tightly, as described, the screws in the split portion of the 
lock nut should be set positively and securely. Only clean 
grease of a kind recommended by the manufacturer should 
be put on the inside of the ball bearing. 

The armature is then ready for insertion in the generator 
frame, and the component parts re-assembled in reverse 
order as previously described for the dis-assembly. Care 
must be exercised to in no way subject the windings to injury 
by contact with other parts. After the assembly has been 
made and the bearing brackets are in position, before putting 
on the outside end caps fill the bracket housings with ball¬ 
bearing grease. Tighten the ball-bearing cap-screws firmly. 
After this re-insert the brushes on the generator in the posi¬ 
tion which they occupied before removal. 

Motor-generator sets shipped complete have a mark indi¬ 
cating the proper position of the generator brush rocker. 
It is possible that a new armature will not operate as suc¬ 
cessfully as the original armature with the brush holders 
set in accordance with this painted mark. In that event it 
will be necessary to move the brush rocker slightly in one 
direction or the other, to first get the point -of sparkless 
operation under load; second, if the full volt and ampere out- 


MANAGERS AND PROJECTIONISTS 


505 


put is then not obtained the rocker may be moved slightly to 
give the desired results while the arc is burning and field 
rheostat three-quarters out if machine is cold. This shifting 
of brush position, however, should never exceed a distance 
more than the width of from one-half to one commutator 
bar. 

THE WOTTON VERTICAL REXOLUX.— This machine is 
made by the Electric Products Company, Cleveland, Ohio. It 
was the first vertical type (armature standing on end) motor 
generator set used for motion picture projection work. The 
Rexolux receives A. C. at line voltage, and delivers D. C. to 
the arc, at arc voltage, without resistance in series and the 
loss incident thereto. % 

The machine is built in three sizes, viz.: One designed to 
operate a single lamp; 
one to operate two 
lamps alternately, and 
one to operate two 
lamps continuously. 

Where two lamps are 
operated continuously, 
only the 70 ampere 
machine is available. 

The 50 ampere ma¬ 
chine, of either MA, 
or twin type (the 
meaning of these dif¬ 
ferent types will be 
explained later o n) 
occupies a floor space 
17 by 20 inches, and 
has a vertical height 
of 34 inches, to the 
top of cap 14, P. 1. 

The switchboard, sup¬ 
ported by angle irons, 
is immediately over 
the machine, so that 
the entire space re¬ 
quired for the 50 am¬ 
pere equipment is 17 
by 20 inches on the 
floor, by 5 feet in 
vertical height. The 



Figure 177. 





















506 


HANDBOOK OF PROJECTION FOR 


35 ampere machine is 3 inches less, and the 70 ampere is 3 
inches greater in height, but the floor space required is 
practically the same for all the types. 

In referring to ampere capacity the ratings are based on 
continuous operation. The 35 ampere machine will carry 50 
amperes, the 50 ampere machine 70 amperes and the 70 
ampere 90 amperes for short periods of time. This means 
that these machines will carry full load continuously, and 
stand the overload named for short periods, say not exceed¬ 
ing two or three minutes. 

These machines are built for all standard voltages and 
frequencies, viz.: 110, 220, 440, and 550 volts; 25, 30, 40, 50 
and 60 cycles, single, two and three phase. 

CONSTRUCTION.— Referring to Piftte 2, Fig. 178, it will 
be seen that the machine consists of four main castings, 
viz.: Base casting 20, which rests directly on the floor and 



Plate 2, Figure 178. 

contains in its center the cup or depression carrying ball race 
6, which supports the entire armature; casting 18, which 
rests on base 20 and forms a housing for the alternating cur¬ 
rent driving motor, the detailed construction of the wind¬ 
ings of which are plainly seen at 19, Plate 2; main upper 
casting 7, which supports the pole pieces of the D. C. gen¬ 
erator, and upper yoke casting 11, carrying grating 23, the 
upper armature bearing, and cap 14, Plate 1 ; main upper 
casting 7, Plate 2, and yoke castings 11, Plate 2, are held to¬ 
gether by bolt 27, Plate 2, dividing at the dotted line. 









MANAGERS AND PROJECTIONISTS 


507 


The armature stands vertical (on end), with the rotor of 
the alternating motor, 4, Plate 2, below, fan 5 above rotor 
4, and armature 1 with commutator 2, above the fan. The 
upper end is supported laterally by a ball bearing, the con¬ 
struction which is shown in detail in Plate 3, Brush holders 
and brushes 17 are shown in Plate 2. 

The details of upper bearing 3, Plate 2, are shown in Plate 
3, in which 4 and 5 are, respectively, an exterior and interior 
ball race, separated by steel balls 6, part 5, the interior race 
being clamped rigidly to shaft 9, by means of nut 2. Part 4 
is stationary and sets in a recess in the main frame casting, 



the whole being covered by cap 1. Part 7 consists of a cast¬ 
ing which is clamped between interior ball race 5, and the 
shoulder of shaft 9, so that it must revolve with the shaft at 
armature speed. Thte part (7) extends down into oil well 10. 
The oiling action is as follows : Oil well 10 is filled with oil up 
to approximately one-quarter inch of the top of the passage 
containing plug 13. Part 7 revolves at high speed, and, by 
the centrifugal action thus created the oil is forced up 
through passage 3-3, whence by gravity it returns again to 
the well through the bearing, thus flooding balls 6 with a 
continuous stream of oil. 









































508 


HANDBOOK OF PROJECTION FOR 


Thirteen, Plates 1, 2 and 3, is a plug closing the passage 
through which oil well 10 is filled. It is essential that this 
plug be in place and screwed tightly home, else the centrifugal 
action before named will force the oil out and empty the well. 

Plug 12, Plates 1, 2 and 3, is for the purpose of draining oil 
well 10, and this should be done at regular intervals every 
thirty days. After draining the oil well insert plug 12 and fill 
the well with kerosene, start the machine and let it run for, 
say, two minutes, after which drain all the kerosene ouf, 
replace plug 12 and fill the well up with lubricating oil to 
within one-quarter inch of the top of the passage stopped by 
plug 13. 

As the quality of oil to be used, see General Instruction 
No. 3, but: 

CAUTION.—Never, under any circumstances, use the much 
advertised patent oils, as they almost without exception are 
worthless for the lubrication of heavy or high speed machin¬ 
ery. The use of such oils will invalidate the manufacturer’s 
guarantee. 

On the other, or lower end of the armature shaft, is ball 
bearing 6, Plate 2, lubrication for which is furnished by 
grease cup 21, Plates 1 and 2. This grease cup should be kept 
filled with Alco Grease. 

CAUTION.— It is important that either Alco Grease or 
some other high grade cup grease be used, because of the 
fact that if a grease containing any acid is used in cup 21, 
the acid will attack the steel balls, and in course of time de¬ 
stroy their accuracy, thus compelling an unnecessary and 
somewhat expensive renewal of the bearing. 

ARMATURE.— The armature or revolving member of the 
machine is completely assembled into one solid part, 1 to 6, 
Plate 2, in which 3 is the upper and 6 the lower bearing. 
The alternating current rotor, or revolving member, 4, is 
built up of reannealed electrical sheet steel, properly punched 
and assembled on armature shaft 9. The rotor bars are 
driven through the slots a tight fit, the ends electrically 
welded together into a solid mass of pure copper, which 
insures perfect contact, low resistance and a uniform torque, 
or pulling force. Directly above the rotor is fan 5, Plate 2, 
made of sheet steel blades and a solid ring, the blades riveted 
and welded together, and finally attached to shaft 9 by means 
of two heavy set screws. This fan produces a suction 
through the ventilating openings in castings 18 and 20, draw¬ 
ing cold air over the windings of the A. C. motor. This air 


MANAGERS AND PROJECTIONISTS 509 


is then forced up over this D. C. armature, and out through 
openings 23, Plate 1. 



Part 1, Plate 2, is the D. C. armature, which is mounted 
directly above fan 5. Armature coils are fixed in place with 
retaining band wires where the connections are made to com¬ 
mutator 2, Plate 2. The commutator is made up of hard 
drawn copper segments, insulated with mica, and held in 
place with steel rings clamped with four bolts. The D. C. 
generator is of the four-pole type, and is provided with com¬ 
mutating or inter poles. 

BRUSHES. —The setting of the brushes is shown in Plate 
4. There are four brush studs, 17, Plate 1, and two brushes 
to a stud. These brushes are attached to the holders by cop¬ 
per “pigtails.” Particu¬ 
lar care should be ex¬ 
ercised to see that the 
screw holding the pig¬ 
tail to the brush holder 
is kept set up tight, 
because unless the pig¬ 
tail makes good contact 
with the holder, the 
tension spring will be 
compelled to carry cur¬ 
rent, which would prob¬ 
ably heat the brush 
spring and destroy its 
temper. 

With regard to the 
amount of tension the 
brushes should have see 

General Instructions Plate 4, Figure 180. 

No. 7. 


The brushes are held in place by a curved arm passing 
around the holder, ending in a tension finger fitting on the 
top of the brush. The brushes are held to the commutator 
against the direction of rotation. The amount of tension can 
be adjusted by the spring and ratchet on the side of the brush 
holder. 

CARE OF COMMUTATOR.— With regard to the care of 
the commutator, see General Instruction No. 7. 

The A. C. driving motor is the induction type, and is built 
either for single, two or three phase current, but the same 
machine will not operate on different phases. All standard 
machines are built to operate on both 110 and 220 volts. 



510 


HANDBOOK OF PROJECTION FOR 


INSTALLATION. —See General Instruction Nos. 1 and 2. 

The Rexolux is so built that it may be readily disassembled, 
since owing to its weight it would in many cases be difficult 
to hoist it in place in a projection room as a unit. In order 
to disassemble the machine, proceed as follows : 

First, open gratings 23, Plate 1, and remove the commutator 
brushes from their holders, allowing them to hang by their 
pigtails so that you can make no mistake in getting them 
back into their proper holder. Remove screws 26, holding 
cap 14, Plate 1. Remove nut 2, Plate 3. Remove nuts 24, 
Plate 1 (three of them) holding main upper casting 7, and 
main lower casting 18 together. Thrust pieces of gas pipe or 
steel bars through the eye-bolts and lift main casting 7 
straight up and off, laying it to one side, but right side up so 
that oil will not run out of oil well 10, Plate 3. Next carefully 
lift out the armature, first, however, having provided two 
blocks or chairs, and lay the same down flatways on these 
blocks or chairs, so that the weight is entirely supported by 
the shaft. 

It is very important that you do not lay the armature down 
so that it rests on the side of the alternating current rotor 4, 
fan 5, or direct current armature 1, or commutator 2, since 
any injury to these would be a very serious matter indeed. 
Handle the armature carefully and use a little good sense, 
if you wish to avoid trouble. The machine may now be 
hoisted or carried into the projection room, where its reas¬ 
sembling will merely be a reversal of the process of disas¬ 
sembling. First carefully lower the armature into place, 
being careful that alternating current rotor 4, Plate 2, be on 
the lower end. Next replace casting 7, and tighten up nuts 
24, Plate 1, tight. Replace top ball races and nut 2, Plate 3, 
tightening nut 2 down as tight as you can get it. Replace 
cap 14 and screws 26. Rotate the armature by hand to see 
that it turns freely, after which replace the brushes in their 
holders, put gratings 25, Plate 1, back into place, and the job 
is done. 

Be sure and wipe the inside of the top casting clean, since 
if any oil should get on it, it would collect the copper dust 
from the commutator and might cause a ground on the brush 
yoke. See that the casting and brush yoke are thoroughly 
cleaned of all oil and dust before it is put back in place. It 
would be preferable to wash them with a cloth dipped in gas¬ 
oline, wiping with a clean, dry cloth afterward. 

Bolts 29, Plate 1, hold pole piece 8, Plate 2, which carries 
coil 9, Plate 2, in place, and should not be removed under any 


MANAGERS AND PROJECTIONISTS 


511 


circumstances,, unless the coil be damaged and require re¬ 
winding. There are four of these pole pieces and eight bolts, 
two bolts per pole piece. Bolts 30, Plate 1, hold inner poles 
10, Plate 2, in place, and should not be removed under any 
circumstances unless the coil is burned out and requires re¬ 
winding. 

Remember the switchboard sets directly over the machine, 
as shown in Plate 1. With each machine there is furnished 
three cork pads, 2 inches square by 1 inch thick, which are to 
be placed under the feet of the machine, where they act as 
a cushion, absorbing noise and vibration. It is not necessary 
nor do we recommend screwing the machine to the floor with 
lag bolts. Its weight is sufficient to hold it in place. 

ELECTRICAL CONNECTIONS—TYPE MA SINGLE ARC 

REXOLUX 

In Plate 5, lines G-G show the direct current circuits. The 
current from the positive generator brush passes out at 
+ G, thence over the evenly dotted line to switch B (G, 
Plate 1), which when closed, connects, after passing through 
the ammeter, with the positive carbons of the arc lamp. 
From the negative brush of the generator the current passes 
through the various interpole coils in series, then out at — G 
thence similarly up to the negative side of switch B, and 
thence to the arc. In order to obtain the necessary field 
regulation, the extra lead from the shunt field is brought 
through the frame at F, Plate 5, and thence up to the field 
regulating resistance. The voltmeter is connected across the 
terminals of the arc at the right hand side of switch B. This 
completes the direct current connection for the type MA 
single arc Rexolux. 

Were it not necessary to obtain a self-starting motor, in 
single phase machines, it would then require but one set of 
windings. In order, however, to obtain the necessary start¬ 
ing torque, a second' set of wire coils is superimposed upon 
the main power coils. This set of starting coils is thrown 
out of phase with the power coils by inserting in series 
therewith a starting resistance and reactance, shown opposite 
starting switch A, Plate 5. The main power coils terminate 
in the frame at “Ml” and “M2,” Plate 5, and the terminals 
of the extra starting coil at T, the other end of which is 
connected inside of the machine to the main power coils. 
The lines designated by a dash and a dot constitute the 
alternating current wiring of the system. 

Where two or three phase current is supplied it is not 


512 


HANDBOOK OF PROJECTION FOR 



Plate 5, Figure 181. 
































































MANAGERS AND PROJECTIONISTS 


513 


necessary to use the extra starting coils, or the starting re¬ 
sistance or the reactance. In this case the wiring incident to 
the starting features of the single phase motor is omitted. 

TWO ARC, TWIN TYPE REXOLUX.— The twin type ap¬ 
plies to all of those equipments wherein two separate motor 
generators are used for two projection arcs. Each motor 
generator is continuously operated independently of the 
other. Each, motor generator is connected to its own pro¬ 
jector. 

Wherever it is desirable to secure double the capacity of 



Plate 6, Figure 182. 


one machine, the two motor generators can be operated in 
parallel by closing the paralleling switch. In case one of the 
motor generators for any reason is out of commission, the 
two projectors can be temporarily handled by the remaining 
machine by stealing the arc from one to the other during 
the change over. By means of these two independent units, 
one reel can be perfectly dissolved into the other without in 
any way affecting the picture on the screen. In the opera¬ 
tion of the twin type there are no switches on the control 
panel which need* to be opened or closed during the change 




514 


HANDBOOK OF PROJECTION FOR 


from one reel to another, or at any other time during the 
performance, except at its beginning and end. One machine 
naturally will be running idle while the arc to which it is 
attached is dead. The actual current consumed by this 
machine is approximately 350 watts. The opening of the 
projector table switch not only disconnects the generator 
from the arc, but opens the field circuit of the generator as 
well. There' is no change over resistance loss with the twin 
type, 


TOO MANY MEN HAVE A WISH¬ 
BONE INSTEAD OF A BACK¬ 
BONE. 



MANAGERS AND PROJECTIONISTS 


515 


Mercury Arc Rectifier 

T HE mercury arc rectifier is a device marketed by two 
manufacturers, the General Electric Company and the 
Westinghouse Electric and Manufacturing Company. 
Its purpose is to change alternating current of standard line 
voltage to direct current at arc voltage, the reduction in pres¬ 
sure being accomplished by means of an auto-transformer, 
which is an integral part of the machine. 

Kindly understand that we have, to some extent, sacrificed 
strict technical correctness to “understandableness” in the 
following: 

PRINCIPLE OF OPERATION. —The mercury arc rectifier 
consists essentially of a sealed glass bulb, from which the air 
has been exhausted, provided with four terminals, A, Al, B 
and C, Fig. 183. Within this tube is a quantity of mercury, 
the purpose of which will be explained further on. The two 
uppjer terminals A. Al. Fig. 183, are of graphite or other 
suitable material, the two lower ones B, are of mercury, 
C, Fig. 183, which is the smaller of the two, being what is 
known as a “starting terminal.” When the bulb is in a 
vertical position the pools of mercury in terminals B and C 
are separated, but when the tube is tilted or rocked side- 
wise to the left, they are brought temporarily into contact, 
for the purpose of starting the tube into action. 

When in its active state the vacuum bulb contains vapor 
of mercury, which is a conductor of electricity only under 
certain conditions. Current will readily pass from graphite 
terminals, A or Al, Fig. 183, into the mercury vapor, and when 
the arc is burning and the circuit thus completed, will pass 
from it into mercury terminal B, and thus on through the 
arc. 

Alternating current, however, changes its direction many 
times in the course of a second of time, and when the direc¬ 
tion of flow seeks to reverse itself and pass from the mer¬ 
cury to the graphite terminals, these terminals offer sufficient 
resistance to prevent it. The graphite terminals thus act as 
check valves, permitting the current to pass from the graphite 
into the mercury vapor, into the mercury and on through the 


516 


HANDBOOK OF PROJECTION FOR 


arc, but preventing it from reversing its direction and passing 
into the graphite terminals. 

The A. C. supply circuit is connected to graphite terminals 
A and Al, Fig. 183, through an auto-transformer, which 
lowers the voltage to that required at the arc, and as the above 
described action will only allow current to flow in one direc¬ 
tion, the pulsations of current which pass alternately from 
terminal A and Al, Fig. 183, into the mercury vapor must, of 
necessity, all pass out of the vapor through mercury terminal 
B, Fig. 183, which is connected to the arc lamp. As a result 
the arc receives a continuous, slightly pulsating current 
which differs but little from ordinary D. C. Ordinarily the 
pulsations would be quite pronounced, but this is prevented 
by a feature of the auto-transformer (main reactance) which 
decreases them to such an extent that the current delivered 
at the arc has a very nearly constant potential value. 

Before the bulb starts working it contains no mercury 
vapor. Within the bulb is a vacuum which must be filled 
with mercury vapor before current can flow. Once the 
space is filled with mercury vapor, however, and current flow 
has been started, it will continue to flow as long as it is un¬ 
interrupted, but any interruption, even for the shortest period 
of time, permits the vacuum to re-establish itself and stops 
the operation of the bulb. 

HOW THE BULB IS STARTED.— In order to fill the bulb 
with mercury vapor, it is tilted until the mercury in terminals 
B, C, comes into contact, and since terminals B and C have 
direct connection with the A. C. supply, through a special 
circuit, current flows between terminals B and C. The tube 
is then rocked back to upright position which breaks the 
mercury bridge thus formed between terminals B and C, and 
in breaking it forms an arc or spark, which creates the 
initial current-carrying mercury vapor, and puts the tube 
into operation. Once started the rectifier will continue to 
operate indefinitely as long as there is no interruption. 

The alternating current supply circuit is connected to an 
auto-transformer, or main reactance, the terminals of which 
are connected to the terminals A, Al, Fig. 183. From ter¬ 
minal B the current passes through the arc, and the circuit 
is completed through a connection to the middle point of the 
auto-transformer. 

The principal parts of a rectifier are: (A) an auto-trans¬ 
former; (B) a regulating reactance coil; (C) a tilting mech¬ 
anism; (D) a relay; (E) a dial switch; (F) a switch or other 


MANAGERS AND PROJECTIONISTS 


517 



means for connecting the auto-transformer directly to the 
arc, and, (G) a bulb and its holder. 

The reactance coil is for the purpose of steadying the arc, 
and limiting the current when the carbons are brought to¬ 
gether when striking an arc, which is a dead short circuit, 
to a value which will not be injurious to the bulb. 

Modern rectifiers are so equipped that in case the bulb 
gives out the projectionist can switch over to the auto¬ 
transformer and continue the show with alternating current, 
using the auto-transformer as an economizer. Also modern 
rectifiers are equipped with a dial switch by means of which 
the projectionist may instantly vary the amperage., within 
the minimum and maximum capacity of the bulb. 

INSTALLATION. —Rectifiers are ordinarily received in two 
separate shipments, one of which, the rectifier itself, weigh¬ 
ing several hundred 
pounds, will probably 
come by freight. The 
other, the glass bulb, 
carefully packed in a 
specially made case, 
is usually sent by ex¬ 
press. In removing 
the bulb from its crate 
proceed strictly ac¬ 
cording to directions 
in loosening the crate, 
after which carefully 
lift out the bulb. It 
will be in an inverted 
p o s i ti o n. Turn it 
slowly over and care¬ 
fully let the mercury 
run down into termi¬ 
nals B, C. In rolling, 
the mercury should 
make a sharp, crack¬ 
ing sound, which is an 

indication that the Figure 183. 

tube is in good con¬ 
dition. 

The rectifier should not be located directly in the projec¬ 
tion room, unless there be some means provided for covering 
the bulb so that its light will not shine in the room. Light in 
the projection room is highly objectionable. One very good 





518 


HANDBOOK OF PROJECTION FOR 


method is to install the rectifier in an adjoining room and cut 
a space through the wall just large enough to admit the front 
panel of the rectifier. This allows the projectionist to have 
access to the switches for the purpose of varying the amper¬ 
age, or changing over to A. C., and at the same time excluding 
the light from the room. Another way is to paint the bulb 
black, using lampblack ground in oil, thinned with turpen¬ 
tine. This does not in any way injure the bulb. It is in fact 
good for it as it will radiate the heat better. 

There is but little sound from a rectifier except a hum¬ 
ming sound which comes from the transformer. Care should 
be exercised that there is no sheet metal near the machine. 
If there is the magnetic action of the transformer will 
probably set up vibration therein, which will cause more or 
less objectionable noise. 

VENTILATION. —There must be ample ventilation where 
the rectifier is located. Lack of ventilation will operate to 
greatly shorten the life of tubes. 

CAUTION.—Tubes should never, under any circumstances, 
be operated above their maximum capacity. 

COMPARATIVE RESULTS. —Experiments by Simon 
Henry Gage and Henry Phelph Gage, Cornell University, 
have shown that the losses through the pulsation of the 
current with the mercury arc rectifier are very slight. A 
mercury arc rectifier using 40 amperes at 52 volts gave 12- 
150 C. P., whereas straight D. C., 40 amperes at 51 volts, 
with the same carbon set, only gave 12,350 C. P., a difference 
of about 200 C. P. 

On page 533 you will find a chart indicating the vari¬ 
ous troubles one is likely to encounter when operating a 
rectifier, together with the most probable cause or causes of 
each. We recommend a careful study of this diagram. With 
this chart and the detailed instructions contained in this 
book, plus a fair supply of common sense, I believe any 
projectionist ought to handle a rectifier without serious 
difficulty. 

GENERAL ELECTRIC MERCURY ARC RECTIFIER.— 

The General Electric Company, Schenectady, N. Y., manu¬ 
factures rectifiers for use on projection circuits in two 
capacities, viz.: 30 and 50 amperes. 

Fig. 190 illustrates the design of the G. E. rectifier fur¬ 
nished for the first time in 1910. Several hundreds of these 
older rectifiers are still in service, and in response to many 
requests we are giving instructions on them. Cuts of the 


MANAGERS AND PROJECTIONISTS 


519 


old rectifier are shown in Fig. 190. Diagram of connections 
is shown in Fig. 191. 

The General Electric rectifiers may all be used on either 
110 or 220 volts. They are made for all commercial cycles 
from 50 to 133, and for 25 to 40 cycle circuits. The late 
type G. E. rectifier is shown in Fig. 184. On the front of the 
panel are mounted the fuses, a three-pole, double-throw 
switch, the adapting links, the dial switch, and either an 
ammeter and voltmeter, or either one singly, these instru- 



High 


Dial 


Mam Reactance 


/ 

Fuses' 


Figure 184. 





520 


HANDBOOK OF PROJECTION FOR 


ments only being provided when especially ordered. On the 
back of the board, or panel, are mounted the regulating 
reactance, the various relays, current limiting resistances, 
tube, etc., as in Fig. 185. 

The machine is not excessive in weight, occupies but little 
floor space, and is entirely automatic in its operation, lo 



Tube 


Starting Ainoc/e 


Co// 

Core 


C. Terminate 

Series Underload 
/?e/ay 

Current Limiting 
Resistance 


Regulating 

Reactance 


Main Reactance 


Figure 185. 

start the rectifier, all that is necessary is to close the A. C. 
supply and projector table switches, and bring the carbons of 
the lamp together. The rectifier will then automatically 
start. 

VOLT AND AMMETER. —The volt and ammeter (when 
ordered) are of the D’arsonval, or permanent magnet type. 













MANAGERS AND PROJECTIONISTS 


521 


They are accurate and are connected in the secondary, or D. 
C. side, hence show the voltage and amperage at the arc. 
They should always be ordered when a rectifier is purchased. 
The better practice is that they be mounted on the wall in 
front of the projectionist, rather than on the rectifier, which 



Figure 186. 

General Electric Mercury Arc Rectifier 


latter, probably, will not be placed directly under the pro¬ 
jectionist's eye. These instruments may be removed from 
the rectifier and so mounted if desired. 

FUSES.—Fuses of greater capacity than those furnished 
with the rectifier should never be used. For a 30 ampere 











522 


HANDBOOK OF PROJECTION FOR 


rectifier use 35 ampere fuses; for 40 or 50 ampere machine 
use 55 ampere fuses. 

FROM DIRECT CURRENT TO ALTERNATING CUR¬ 
RENT. —In Fig. 184 we see a triple-pole, double throw 
switch in the center of the panel. By throwing this switch 
over the tube is cut out and A. C. direct from the lines is 
supplied to the arc, using the main reactance as an economi¬ 
zer. This is for use in case of accident to the tube. The 
switch as shown in Fig. 184 is set for D. C. 

If the switch is thrown over to A. C. it may be found 
there is not sufficient amperage, in which case lead 3, Fig. 
186, may be moved along studs 1, until sufficient current is 
obtained. Do not use more than 60 amperes, A. C. The 
rectifier is built primarily for changing A. C. to D. C., and, 
while its main reactance may be used as an economizer, that 
provision is designed for emergency only. 

CONNECTING OR ADAPTING LINKS.— The connecting 
or adapting links, Fig. 184, enable the rectifier to use either 
110 or 220 volt supply. To change from one to the other it 
is only necessary to change the connection of the links. For 
220 volt supply they should be connected to the two upper 
and the two outer lower studs; for 110 volt supply connect 
to the two upper and the two inside lower studs. 

THE DIAL SWITCH. —The dial switch has eleven con¬ 
tacts which are connected to eleven taps on the regulating 
reactance, Figs. 185 and 186. This connection may be exam¬ 
ined in Fig. 186, in which the regulating reactance, 2, has 
been dropped down to show the connections. This switch 
enables the projectionist to regulate the amperage at the 
arc, and any amperage within the capacity of the rectifier 
may be instantly had by merely moving the switch to the 
left to raise, or to the right to lower, as per Fig. 184. 

THE MAIN REACTANCE, Fig. 184, is nothing more nor 
less than an auto-transformer. It has three distinct func¬ 
tions, viz.: (a) It adjusts the voltage of the alternating 
current to the pressure necessary to secure the proper D. C. 
amperage at the lamp; (b) it supplies a neutral point be¬ 
tween the alternating current lines and forms the negative 
of the direct current lines ; (c) by its reactance it keeps- the 
rectifier tube in operation while the current passes through 
the zero point of the alternating current wave. 

THE REGULATING REACTANCE. —The regulating re¬ 
actance, Figs. 185 and 186, is nothing more nor less than a 


MANAGERS AND PROJECTIONISTS 


523 


choke coil, with eleven or more taps taken off at certain 
points along the winding. These taps are connected to an 
equal number of contacts of the dial switch, Fig. 184, so 
that the alternating current can be choked back or reduced 
to a value just sufficient to give the desired amperage at 
the arc. 

Fig. 187 is a diagram of the connections of the General 
Electric mercury arc rectifier; all parts of the rectifier are 
shown diagrammatically without reference to their actual 



position with relation to one another when mounted on the 
rectifier, the idea being merely to illustrate the method em¬ 
ployed in starting. It will be seen that three coils are used 
for starting, viz.: A shaking magnet, a series underload re¬ 
lay and a starting anode relay, the latter, which is normally 
open, but picks up when the carbons of the lamp are 
brought together, thus closing the shaking magnet circuit 
































524 


HANDBOOK OF PROJECTION FOR 


(see D, Fig. 187), whereupon the shaking magnet pulls the 
tube over to one side, or, in other words, “rocks” it, thus 
allowing the mercury in cathode B, Fig. 183, to bridge over 
and form a connection with the mercury in starting anode C, 
which shunts the current from the starting anode relay D, 
Fig. 187, circuit, and operates to demagnetize its coil, thus 
allowing its plunger to fall and open the shaking magnet 
circuit, whereupon the tube, by its own weight, rocks back 
into vertical position, thus breaking the mercury bridge be¬ 
tween anode C and cathode B. After the tube has started 
operating, and the arc has been struck, the series under¬ 
load relay which is connected in the D. C. circuit picks up, 
thus cutting the starting anode relay and shaking magnet 
entirely out of circuit. If the tube does not start at once 
the shaking magnet will continue to rock the tube until it 
does. 

INSTALLATION. —After the rectifier set has been un¬ 
crated and placed in its operating location (see “Installa¬ 
tion,” page 517), the tube should be placed in the holders 
E, F, as per Fig. 185. This is accomplished by pressing the 
narrow part of the tube, just above anode arms A, Al, Fig. 

183, into upper clip E, Fig. 185, carefully lowering the tube 
until anodes A, Al, Fig. 183, rest on the lower clips, F, Fig. 
185. Having the tube in place, you will find four wires 
covered with a sort of glass bead insulation, these wires 
terminating in brass spring clips, Fig. 188. Connect the two 
upper ones (either one to either anode) to anodes A, Al, the 
small lower one to starting anode C, Fig. 183, and the large 
lower one to cathode B, Fig. 183, as shown in Fig. 185. Next 
connect the A. C. supply lines to the two terminals, marked 
A-C, at the upper left-hand corner of the panel—that is to 
say, the left-hand corner as you stand facing the tube on 
the back side of the machine. Next connect the positive D. 
C. terminal, Fig. 185, marked + to one side of the projector 
table switch, and through the projector table switch to the 
upper carbon arm of the lamp, and connect the negative 
(marked) D. C. terminal to the other side of the projector 
table switch, and through it to the lower carbon arm of the 
lamp. Connect the adapting links in the front of the panel 
according to the voltage of your alternating current supply, 
as already directed. Having accomplished all this, with the 
triple-pole switch closed in the upper position, as per Fig. 

184, and with the A. C. supply and D. C. projector table 
switch closed, the rectifier is ready to start. 


MANAGERS AND PROJECTIONISTS 


525 


OPERATION. —To start the rectifier bring the lamp car¬ 
bons together, the tube will rock, and will either start or 
continue rocking. As soon as it starts, slowly separate the 
carbons to the usual distance for a D. C. arc. When the 



Figure 188. 














526 


HANDBOOK OF PROJECTION FOR 


carbons have been separated so that the voltage between 
them is about 45, the potential relay 4, Fig. 188 (if it is a 40 
or 50 ampere rectifier; there is none on the smaller size) 
will operate and short-circuit current limiting resistance 3. 
Fig. 188, thus increasing the arc current to whatever value 
the dial switch is set for. 

CAUTION. —When you first begin to use a rectifier be 
sure that the potential relay operates. If it does not, cur¬ 
rent limiting resistance, 3, Fig. 188, will heat, and while it 
would be difficult to actually burn it out, damage might be 
done to it or to the insulation of surrounding wires. 

The projectionist can tell when this relay acts, as follows: 

When the carbons are 
first separated the 
current will be com¬ 
paratively * weak, but 
when the relay acts 
there will be a sudden 
increase in brilliancy 
at the spot. The knack 
of detecting the acting 
of the relay can be 
acquired by starting 
the arc several times 
and slowly separating 
the carbons until the 
relay picks up, having 
a man at the rectifier 
to tell you when it 
does pick up in case the reetifier is at a distance. 

To stop the rectifier, open the projector table switch, 
though opening either the switch on the A. C. lines or the 
triple-pole switch in the face of the rectifier panel will have 
the same result. 

OPERATING TWO ARCS FROM ONE RECTIFIER.— 

When it is desirable to operate two arcs from one rectifrer 
the General Electric Company will furnish two resistances 
equipped with contactors, one to be used in series with each 
lamp. These resistances consist of a number of coils, in¬ 
closed in a ventilated sheet metal box, for mounting on the 
frame or standing on the floor beside the machine. 

Diagram, Fig. 189, shows the resistance connected in the 
lamp circuits. The operation of dissolving one reel into an¬ 
other is briefly as follows: Assume the projectionist to be 


Rectifier Terminals 

+ 
















MANAGERS AND PROJECTIONISTS 


527 


running a picture on projector No. 1, in which case the con¬ 
tactor is closed by hand (thus cutting out the resistance 
which is normally in circuit) at the start and is then held 
closed by a magnet coil. At any time while this reel is run¬ 
ning the projectionist (leaving the contactor on arc No. 2 
open) may start projector No. 2, at about 10 amperes, thus 
allowing the carbon to be warmed up on No. 2 while the reel 
is still being run on projector No. 1. At the end of the reel 
on projector No. 1, projector No. 2, with arc burning with 
resistance in circuit, is then started, and the contactor closed, 
thus cutting out the resistance and boosting the current to 
normal, at the same time short-circuiting the arc of pro¬ 
jector No. 1 and putting it out, which stops the current flow 
in resistance box No. 1, thus opening the contactor. The 
resistance cannot be accidentally left out when the second 
arc is struck. When the first arc is short-circuited the con¬ 
tactor opens, which automatically cuts in the resistance. 
These resistances prevent overloading the rectifier. Re¬ 
member that the resistance is in when the contactor is 
open. 

We would most emphatically recommend to exhibitors the 
purchase of the large rectifier. Modern practice is to use 
high amperage and project a brilliant picture. The first cost 
will be greater, but it is well worth the money. This holds 
good even for the small towns, provided sufficient current is 
available to supply the large rectifier. 

PRACTICAL OPERATION.— You need not be afraid to 
perform any of the various operations we shall describe in 
case of necessity. Just follow the directions and use a 
little common sense, remembering where each part goes, or, 
better still, attaching a labeled tag to it as you remove it. 
There is no mystery about these things. All too often the 
projectionist hesitates to attempt the making of repairs 
through fear of being unable to get the thing back into 
shape. The rectifier is strongly made; its parts are very 
simple. We repeat: Follow the instructions here given, 
supplementing them by ordinary common sense, and you 
will not be likely to have any trouble. 

Current-limiting resistance 3, Fig. 188, consists of a strip 
of resistance metal, wound in spiral form, covered with in¬ 
sulating material and supplied with contacts at either end. 
Resistances 1 and 9, Fig. 188, are of wire wound on asbestos, 
the whole dipped in an insulating material. 

The purpose of current-limiting resistance 3, Fig. 188, is 


528 


HANDBOOK OF PROJECTION FOR 


as follows: When the lamp carbons are brought together 
the effect is, to all intents and purposes, to form a short 
circuit, which would have the effect of sending a heavy rush 
of current through the arc circuit. Resistance 3, Fig. 188, 
takes the place of the resistance the arc will offer after the 
carbons are separated. This resistance is automatically cut 
into circuit when the plunger of relay 4, Fig. 188, is down ; 
or, in other words, when relay 4 is “open.” When the car¬ 
bons are opened and the arc struck, the effect is to add the 
resistance of the arc to the resistance offered by current- 
limiting resistance, 3, and thus raise the voltage of the lamp 
circuit. When this voltage reaches a certain point (about 40 



Figure 189a. 


volts) the energy of the magnet of relay 4 becomes suffi¬ 
cient to raise plunger 5, Figs. 188 and 189, and bring blade 6, 
Figs. 188 and 189, into contact with block 7, Figs. 188 and 
189, thus short-circuiting current-limiting resistance 3, and 
raising the D. C. amperage. 

Should relay 4 at any time fail to act, it is likely plunger 
5, Figs. 188 and 189, is stuck, which might be caused by a 
grain of sand, a bit of dirt or from some other cause. This 
plunger may be removed from the magnet by pulling out 
split key 18, Figs. 188 and 189, and, while holding stationary 
nut 9 at the top of the plunger, unscrew plunger 5 by turn¬ 
ing its lower end. Having removed the plunger and ascer¬ 
tained the cause of its sticking it may be replaced, and when 
you are able to get split key 18 into its hole the plunger is 
in the proper location. In replacing nut be sure to get it 








MANAGERS AND PROJECTIONISTS 


529 


right side up. If you cannot get the split key in, the prob¬ 
ability is that you have the nut wrong side up. Also, in re¬ 
placing nut 9, be sure to get the two washers underneath it 
in place. 

It will be well to clean the contact between block 7 and 
blade 6, Fig. 189, about once a month, using 00 emery cloth. 

Should anything occur to seriously injure the parts on top 
of relay 4, Fig. 189, as for instance something falling on 
them and smashing the whole thing so badly that it could 
not readily be put back into shape, then new parts can be 
obtained from the factory. In order to remove the old parts, 
take out three screws in the top of block 10, Fig. 189, the 
same being countersunk into the block, two on one side of 
the brass parts and one on the other; disconnect the wires 
from the parts ; take out plunger 5, as per former directions. 
You can then lift the block off and replace it with a new one. 
The block should be ordered complete, with the parts as¬ 
sembled. Should it ever become necessary to remove the 
coil of relay 4, Fig. 189, first proceed, as before directed, to 
remove block 10, Fig. 189, whereupon you will see three 
screws in the top of the coil casing. Remove them, discon¬ 
nect the two wires which lead from the coil, and disconnect 
wires (two of them) X, Fig. 189. You may then lift the coil 
out, and replace it with a new one if necessary. 

The instructions given for removing the top and the coil 
of relay 4, Fig. 189, apply equally to all the other relays; 
just remove the screws in the top of the block (the screws 
are, in all cases, countersunk), disconnect the wires, remove 
the relay plunger, and the whole thing comes off. 

Resistance coil 9, Fig. 188, is connected in series with the 
contacts of series underload relay 11, Figs. 188 and 189. (You 
cannot see this relay in Fig. 188. It is under arrow head 
11). This resistance is not in series with the relay coil, but 
serves to limit the flow of current through the starting 
anode, Fig. 185. But for this resistance the flow of current 
through the starting anode would be so heavy that there 
would be liability of damage to the tube. 

Resistance coil 1 and 9, Fig. 188 may be removed simply by 
pulling them out of their clips as you would a cartridge 
fuse. Resistance coil 3 may be removed by disconnecting 
the wires attached to it, and taking out the screw which 
holds the carrying clip to the panel. 

SHAKING MAGNET— The action of the rectifier is made 
automatic by means of shaking magnet 13 and relay 8, Figs. 


530 


HANDBOOK OF PROJECTION FOR 


188 and 189. These magnets are therefore very important. 
Part 15, Figs. 188 and 189, is so made that it brings the tube 
back to the vertical position after it has been rocked by the 
action of the shaking magnet, through force of gravity. 
Should the tube at any time fail to rock to the vertical 
position, it is most likely due to friction in spindle 16, Figs. 
188 and 189. This friction may be overcome by means of a 
drop or two of oil on the bearing surfaces, just behind the 
nut on the end of the bolt, and at the back of the spindle. It 
is also possible that dirt may work in beside plunger 17, 
Figs. 188 and 189. This plunger may be removed by taking 
out the bolt in the fork at its lower end, and driving out the 
small pin in nut 17 at the top of the plunger. The plunger 
can then be dropped down enough to clean it. 

Should plunger 20 of relay 8, Figs. 188 and 189, fail to 
work, it may be taken out and examined by removing the 
split key at its upper end and pulling the plunger out at the 
bottom. 

Should the rectifier at any time fail to act, the very first 
thing to examine and test will be your fuses, including those 
on the front of the panel. Don’t try anything else until you 
have tested the fuses. It is quite possible you may get a 
spark at the carbons of the lamp when one of the fuses is 
burned out. 

ORDERING RENEWAL PARTS.— Almost every projec¬ 
tionist will, sooner or later, find it necessary to replace cer¬ 
tain parts of the rectifier equipment that wear out from 
usage. 

IMPORTANT.—To insure correct filling of orders for 
such parts it is essential that the following information be 
given with each order: 

1. Catalog number and 

2. Serial number of complete rectifier equipment. (These 
will be found stamped upon name-plate attached to front of 
rectifier panel.) 

3. Catalog number, specification or any distinguishing 
mark that may appear on the part wanted. 

3A. If no marking can be found, describe the part ae 
clearly as possible. An accurate pencil sketch of the par- 
helps, too. 

4. Quantity of each part wanted. 

The order should then be forwarded to the nearest sale: 
office of the General Electric Company, or direct to its Gen 
eral Offices at Schenectady, N. Y. 


MANAGERS AND PROJECTIONISTS 531 

OLD STYLE MERCURY ARC RECTIFIER.— The follow- 
ing information is prepared for the convenience of projec¬ 
tionists using G. E. Rectifiers of the design furnished prior to 
1918, many of which are still in use, particularly in the west. 

Before putting this information to use it is well to com¬ 
pare your panel with illustrations shown in Fig. 190 and to 
determine whether they correspond. 



Figure 190. 


1. The leads marked “AC” should be connected to the 
lower studs of a double-pole switch located near the motion 
picture projector. The upper studs of the switch should be 
connected to the “AC” source of supply. 

2. The leads marked + and — should be connected respec¬ 
tively to the positive (upper) and negative (lower) carbons 
of the motion picture lamp. 

3. If the “AC” supply voltage is 110, then connect the 













532 


HANDBOOK OF PROJECTION FOR 


flexible lead marked “Z” to stud marked 12, and flexible lead 
marked “Y” to stud marked 6 on main reactance. 

If the “AC” supply voltage is 220 volts then connect lead 
“Z” to stud 7, and lead “Y” to stud 1 on main reactance. 
Note: do not disturb the other connections that are made 
on studs 1, 6, 7 and 12 of the main reactance, but only place 
leads “Y” and “Z” as directed. 

4. The tube holder should be reversed so that the clip and 
support will be turned away from the panel instead of 
towards the panel, as it is when shipped. 

WIRING DIAGRAM FOR OLD STYLE RECTIFIERS.— 
5. Remove the tube from its box, being very careful not 
to handle it roughly, nor to strain the seals in any way 
whatever. Care must also be taken to prevent the mercury 
from suddenly flowing into any of the arms, otherwise the 



Back View of Rectifier panel Showing Wiring 

Figure 191. 





























































MANAGERS AND PROJECTIONISTS 


533 


H 

01 

< 

B 

ai 

B 

o<! 

£ 

t/i 

w 

o 

Q 

w 

« 

B 


i f i 


rt 


RECTIFIER TROUBLE CHART. 

("Current at switch—Fuses blown. 


No 


current at 
terminals. 


tube 


V.C/2 


c/n 

B 


W 

B 


No current at switch—Line voltage off. 
/-Friction or bent stud. 


Relay contact not closed.< 


Relay contact is poor. 

Tilting circuit open. 

Secondary coil of magnet short 
circuited. 


Amalgam bridge between electrodes—Install new tube. 


/•Lamp circuit open. 


D. C. circuit open. 


72 

-H 

uj 

I—I 

B 

w' 

W 

L 

B 


Does not return^ 
to vertical. 


Carbons not making good contact with 
each other or with the lamp jaws. 

Lead on starting anode broken or loose. 

do not make 


Mercury pools 
contact. 


Friction in tube holder. 
Returns to vertical with- ] Tube is defective. 


Adjust tube; it 
does not tilt 
far enough. 


out flash after 
peated tilts. 

Flashes and goes out. 


r 


{ 


New tube. 


Fube has lost its vacuum. 

Lead to positive electrode anode loose or 
broken. 


Tube continues to tilt I Relay does not open J Winding short-circuited, 


after starting 
Tube gees out. 

Tube tilts feebly. 

Outfit is noisy. 


K 


1 


the circuit. 


1 


friction or bent stud. 


amp carbons separated too far. 

Voltage of circuit low. 

Frequency of current not right. 

Friction in tilting mechanism. 

Tube is too heavy at bottom. 

TReactance coil loose on frame. 

Reactance coil air gap not wedged tight. 

Cover vibrates. 

I Operating room floor vibrates—set outfit on felt 
L pads. 

Arc is noisy. j Carbons too hard—use softer ones. 

NOTE—When proper vacuum exists the mercury gives off a sharp 
clicking sound when it is run from one end of the tube to the other. 
Absence of this sound and the presence of air bubbles show loss of 


vacuum. 

Tube may be defective by short-circuiting between starting anode 
and cathode. When in this condition it is badly blackened. 
















534 


HANDBOOK OF PROJECTION FOR 


resultant pound might damage them. Examine the tube for 
vacuum by noting the sound the mercury makes when al¬ 
lowed to roll gently about in the large chamber. If it makes 
a clear, metallic, click, the vacuum is good, but if the sound 
be dull and the mercury sluggish in moving, the vacuum is 
either partially or wholly destroyed. If the vacuum is poor, 
the life of the tube may be short, or it may not start at all. 

To insure careful handling and safe delivery, Mercury Arc 
Rectifier tubes are always shipped by express in the special 
box as they come from the factory. 

6. Place the tube in the holder by inserting the small part 
of the tube just above the anode arms in the upper clip, then 
gently lower it until it rests firmly on the lower support. 
Connect the tube and beaded leads according to diagram, 
Fig. 191. 

7. Adjustment of current (number of amp-eres) at Jhe arc 
is obtained by connecting lead marked “X” to studs 6, 5, 4, 
3, 2 or 1 of the regulating reactance. Stud 1 gives the maxi¬ 
mum and stud 6 the minimum number of amperes. 

In starting up the first time it is best to start with lead 
“X” on stud 6 and move toward the maximum position by 
steps until the desired current is obtained, as indicated by 
ammeter. For this adjustment it is advisable to connect an 
ammeter in series with the arc of the projector. 

8. With the above instructions carried out, all that is 
necessary to start is to close switch in the ‘AC” line, and 
bring carbons of lamp together. The automatic shaking de¬ 
vice should then rock the tube until the tube starts. As soon 
as tube starts separate carbons. 

9. The best and whitest light can be obtained when in. 
cored carbon is used above and y 2 in. solid carbon below, 
being careful not to get solid carbons too hard. 

WESTINGHOUSE MERCURY ARC RECTIFIER.— In 

Plate 1 we get a view of the front of the Westinghouse 
Mercury Arc Rectifier designed for use on projection cir¬ 
cuits. It is built in 30, 40 and 50 ampere sizes, the general 
design, characteristics and appearance being the same for 
all. 

Each outfit consists of a cast iron main frame on which 
is mounted an auto-transformer, L-L, Plate 3; reactance coil, 
Q, Plate 3; a tilting mechanism, B, D, K, P, Plate 2; a relay, 
I, Plate 3; a five-point dial switch, Plate 1, and E, F, G, H, I, 
Plate 2; adapting links, Plate 1; a tube and tube holder, 24, 


MANAGERS AND PROJECTIONISTS 


535 


25, 26, Plate 4, all inclosed in a perforated sheet steel cover. 
The machine occupies but little floor space. 

In Plate 2, we have a view of the rectifier with the per¬ 
forated sheet steel cover, the cover of the dial switch and 
the tube removed. At the bottom, in the corner, is the tilt¬ 
ing magnet, P, the operation of which is very clearly shown. 
When magnet P is energized, its plunger, K, moves down¬ 
ward and tilts or rocks the tube. The construction of the 
dial switch is also very clearly shown, the round buttons, E, 
being dummies, over which switch contact fingers G slide 



ADAPTING 


dial 


SWITCH 


LINKS 


INSTRUCTION 
CARD 


FRONT 
PERFORATED 
COVER 


INSTRUCTION 
CARD 
IF RAME 


Plate 1, Figure 192. 























536 HANDBOOK OF PROJECTION FOR 


from one wide contact, F, to another. At the bottom are 
four wires, L, M, N, O, coiled up and terminating in brass 
spring clips. These are the leads which connect to the 
anodes and cathodes of the tube, as per 9-9-12-29, Plate 4. 

In Plate 3 we have a rear view of the outfit, showing, near 
the bottom, the reactance Q, and above it the auto-trans¬ 
former L-L. In Plate 3 we see at the left the D. C. leads, 


Plate 2, Figure 193. 

A, mounting screws for relay; B, upper bulb spring holder; C, lower 
bulb spring holder; D, brass guide for tilting rod; £, dummy contacts; 
F, contacts; G, contact finger; H, contact arm; I, insulating support for 
contact; J, bulb holder casting; K, tilting magnet plunger; L, M, N, O, 
wires- having spring contacts at end to connect to tube anodes and 
cathodes. 






































MANAGERS AND PROJECTIONISTS 


537 


A, B, which connect to the arc lamp circuit, the inside one, 
A, being the negative and the outside or left hand one B, 
the positive. The positive must, of course, connect through 
the projector table switch to the top carbon arm of the lamp, 
and the negative through the projector table switch to the 
bottom carbon arm of the lamp. The A. C. leads, H, are 
seen in Plate 3 at right hand side. These leads connect 
directly, through a switch and fuse, to the alternating cur¬ 
rent supply. In the center, at the top of Plate 3, is relay 
magnet 1, the purpose of which will be explained further on. 

THE AUTO-TRANSFORMER, L-L, Plate 3, consists of 
an iron core with a winding of heavy copper wire. It is 
similar to an ordinary transformer, except that its connec¬ 
tions are such that in effect it has only one winding, where¬ 
as the ordinary transformer has two, viz.: a primary and 
secondary. Its function is to change the voltage of the A. 
C. supply circuit to the pressure required at the arc. The 
center point of the winding also forms the negative ter¬ 
minal of the arc circuit, as per 3, 4, 4, in diagram, Plate 5. 
See Fig. 199, page 546. 

REACTANCE COIL. —The reactance coil, Q, Plate 3, is 
similar in appearance and construction to a transformer. It 
is connected into the alternating current circuit for the pur¬ 
pose of limiting current flow when the carbons are brought 
together to strike the arc, to a value that will not be in¬ 
jurious to the tube; also it operates to insure steadiness of 
the arc and to prevent any wide fluctuations of the current 
when the length of the arc is changed. The general effect is 
to make the arc much easier to handle. 

TILTING MECHANISM. —Each rectifier is provided with 
an automatic tilting device, consisting of parts B, D, K and 
P, Plate 2. This device is so connected that the closing of 
the carbons energizes magnet P and thus causes the tube to 
tilt, which makes the rectifier a self-starter. The mechanism 
is operated by magnet P, Plate 2, the pull of which is applied 
to the tube by coil spring B, Plate 2, as shown. A spring is 
used instead of a rod in order to prevent the tube from 
being subjected to unnecessary and violent shock. 

THE RELAY, 1, Plate 3, is another magnet, used to oper¬ 
ate the contacts which open the tilting magnet circuit when 
the arc is started, thus preventing the tube from tilting at 
any other time. But for this cutout the tilting magnet would 
continue to operate, and the tube would be tilted, or rocked 
continuously. 


538 


HANDBOOK OF PROJECTION FOR 


THE FIVE POINT DIAL SWITCH, Plates 1 and 2, is used 

to change the connections to the reactance coil in such way 
as to vary the arc current to any desired value within the 
limits of the machine. This switch, as its name indicates, 



Plate 3, Figure 194. 


A, positive D. C. lead; B, negative D. C. lead; C, relay contact disc; 
U, transformer lead tags; E, rear end of bulb holder shaft in ball bear- 
mg; b reactance lead tags; G, fibre clamping blocks for reactance coil- 
H, A C. leads; I, relay magnet; J, relay contact stud; K, transformer 
iron; L transformer coil; M, clamping block for transformer iron¬ 
s’ mounting bolt for transformer; P, cotter pin; Q, reactance coil; 
K, reactance iron; S, reactance coil leads. 

































MANAGERS AND PROJECTIONISTS 


539 


gives five different values of current, and the change may be 
made from one point to another without breaking the arc. 

THE UPPER ADAPTING LINK, 17, Plate 4, is for the 
purpose of changing the connections to the reactance coil, so 
as to provide proper voltage adjustment at the arc for dif¬ 
ferent supply circuit voltages. In other words, the A. C. 
supply may be 220 or 110 on the face of it, whereas the 
actual pressure in the theatre, owing to drop in line, etc., 
may be anywhere between 210 and 230, or 105 and 115 volts. 
By means of this link it is possible to provide for these 
variations and make a connection suited to the actual volt¬ 
age, which easily may be determined by using an A. C. volt¬ 
meter. If a voltmeter is not available the lighting company 
should be requested to make the test. 

THE LOWER LINK CONNECTOR, 18, Plate 4, is used in 
emergency, to transfer the arc from the tube circuit to 
direct operation on the alternating current circuit, in case 
the tube should fail or something else happen to the rectify¬ 
ing side of the machine. For direct current operation (recti¬ 
fication) this link should be placed so as to join the lower of 
the three terminals and the upper right hand terminals, 
marked “D. C. Arc”; for alternating current operation the 
link should join the lower terminal and the upper left hand 
terminal marked “A. C. Arc.” Be sure that the wing nuts 
are well tightened so as to clamp the links firmly. 

THE TUBE is a glass vessel into which a small amount 
of mercury has been placed, and from which all the air has 
been removed, causing a vacuum. The general character¬ 
istics of its operation have been described under “General 
Remarks,” page 515. It has four terminals, the upper ones 
being the graphite anodes, the smaller, lower one the start¬ 
ing anode and the larger lower one the cathode; both the 
two low r er are of mercury. These various terminals are 
connected to coiled leads L, M, N, O, Plate 2, by means of 
brass spring clips, as at 9, 9, 12, 29, Plate 4. 

INSTALLATION. —The rectifier will be received in two 
shipments. The glass tube, carefully packed in a special 
crate, is usually sent by express, whereas the remainder of 
the outfit, being the completely assembled rectifier (except 
the tube) all ready for operation, will probably be sent by 
freight. When the outfit is received, remove it from its 
case and place in the location selected. Remove the per¬ 
forated sheet steel cover and connect the A. C. feed wires 
to rectifier leads H, Plate 3, through a line switch and fuses. 


540 


HANDBOOK OF PROJECTION FOR 



Plate 4, Figure 195. 


1, lifting lug; 2, name plate; 3, mounting bolt for slate panel; 4, cast 
iron cover for dial switch; 5, dial switch handle; 6, rear perforated 
cover; 7, cable containing leads; 8, transformer; 9, spring clip on side 
terminal of bulb; 10, mercury pool in bulb; 11, lead to side terminal 
of bulb; 12, spring clip on large lower terminal of bulb; 13, resistance 
box terminal; 14, main cast iron frame; 15, resistance box; 16, stud 
for link connector; 17, upper link connector; 18, lower link connector; 
19, end of relay contact stud; 20, transformer leads; 21, stud for front 
perforated cover; 22, bolt for front perforated cover; 23, mounting 
bolt for transformer; 24, upper bulb holder spring; 25, bulb; 26, lower 
bulb holder spring; 27, mounting strap for tilting magnet and resistance 
box; 28, lug for tilting magnet and resistance box; 29, spring clip on 
small lower terminal of bulb; 30, tilting magnet frame; 31, tilting 
magnet coil; 32, terminal board; 33, connector on terminal board; 34, 
wiring from terminal board; 35, dial switch pointer. 



























































MANAGERS AND PROJECTIONISTS 


541 


as per instructions mounted on front cover of the rectifier. 
Connect leads D — and C -j- to the projector table switch 
with the positive (+), B, Plate 3, connected to the top 
carbon arm and the negative (—), A, Plate 3, connected to 
the lower carbon arm. Open the crate containing the tube 
by removing two screws from the center of each side. Lift 
the outer portion of the crate away, which will leave the 
tube suspended from the inner portion of the crate. Loosen 
the line tape and lift the tube carefully from the holder. 
Turn the tube upside down, slowly and very carefully, 
making sure that the mercury runs slowly into the two 
bottom terminals. The mercury in a tube that is in good 
condition should make a sharp metallic click when passing 
from one end of the tube to the other. Grasp the tube 
firmly in both hands, 
the right at the extreme 
top and the left grasp¬ 
ing the mercury ter- «« 
minals, and, guarding 
carefully against col¬ 
lision, slide the tube 
into the lower spring 
clips of the tube holder, 
taking care that the 
springs do not cause the 
tube to slide into the 
tube holder with a jar. 

Be very careful not to allow the smaller mercury terminal 
to strike the tube holder, or any other object, as it is quite 
easily broken. After the lower part of the tube is properly 
placed, push the top part gently back into the upper spring. 
If it becomes necessary to remove the tube, as in case of 
changing location of outfit, the same method of handling 
should be followed. Connect the tube leads (that is, the 
flexible wires attached to the terminal board below the 
tube marked L, M, N, and O, Plate 2) to the tube, as shown 
at 9, 9, 12, 29, Plate 4. The wires may easily be traced in 
Plate 4. Connect wire 4, Plate 2, to the upper left hand tube 
terminal, 9, Plate 4; the lead M to the small lower tube 
terminal, 29, Plate 4; lead N to the large lower terminal, 12, 
Plate 4, and lead 0, the last one, to the right hand upper 
terminal, 9, Plate 4. The upper link connector on the slate 
panel at the top of the outfit should now be connected to 
suit the voltage of the supply wires, which should be de¬ 
termined by actual test with a reliable voltmeter. It may 



Figure 195a. 






















542 


HANDBOOK OF PROJECTION FOR 


be noted in this connection that the voltage for which the 
link is set should be tested when the rectifier is in actual 
operation, since the voltage of the line may decrease with 
the added load. It is unlikely that once this connection is 
properly made it ever will be necessary to change it. The 
outfit, without any further adjustment, is now ready for 
operation. 

Plate 5 shows the wiring diagram for the three types of 
the Westinghouse rectifier. These diagrams are, we believe, 
of questionable value to the average projectionist. However, 
there are a goodly number who will be able to make use of 
them. The upper one is for the 30 ampere, 110-220 volt, 
the center one for the 40 ampere, 110-220 volt, and the lower 
one for the 50 ampere, 110 volt rectifier. 

OPERATION. —With fuses of proper capacity in place, 
close both the A. C. line switch and the projector table switch 
and bring the carbons together, whereupon the tube will 
rock, a spark appearing between the two mercury pools at 
each tilt until the arc starts, when the whole tube will light 
up and come to rest in a vertical position. The carbons 
should be instantly separated until the greatest amount of 
light is obtained on the screen. 

Where the size of the theatre and equipment only justifies 
the purchase of a single rectifier, the problem of blending 
one reel into the next has been solved as described below: 
The only extra equipment necessary is a compensator or 
economy coil such is is usually found in a theatre using 
alternating current, and a four-pole, double throw switch. 

The wiring is shown in Fig. 195a and requires no elaborate 
explanation. By means of this plan the change-over may be 
made without any very seriously objectionable indication 
of the fact on the screen. The projectionist, we will say, is 
showing the first reel of a feature film on machine No. 1, 
which is fed from the rectifier, the switch being thrown to 
the left. About one minute before the end of the reel is 
reached he throws the switch to the right, starting the arc 
on machine No. 2 through the rectifier, while projector 1 
is transferred to the alternating current supply of the com¬ 
pensator, and the reel is completed in this manner. This 
gives the carbons on No. 2 time to burn to their proper 
brilliancy on D. C., ready to begin the second reel. The 
process is repeated toward the end of the second reel on 
projector 2. The procedure may, if desired, be reversed; 
that is to say, starting machine No. 2 on alternating current 
and later changing it to direct current. However, the first 


MANAGERS AND PROJECTIONISTS 


543 


mentioned will be found more satisfactory, as it takes a 
short while for the direct current to burn the crater properly. 


at oc 



Plate 5, Figure 196. 


































































































































544 


HANDBOOK OF PROJECTION FOR 


The Transformer 


T HE transformer cannot be used on direct current. It is a 
device made entirely for use with A. C. Its purpose is to 
change alternating current of any given cycle (fre¬ 
quency) and voltage and amperage to an alternating current of 
the same cycle, but of different voltage and amperage. 

The transformer assembly consists of four separate ele¬ 
ments, viz.: a laminated core of iron, a primary coil, a 
secondary coil and a protecting casing or covering. In addi¬ 
tion to this there may be other elements, such as an adjusting 
switch by means of which the amperage delivery of the 
secondary coil may be varied. 

In Fig. 197 we have diagrammatic representation of the 

simplest form of trans¬ 
former. The primary 
coil is wound around 
one “leg,” or side of a 
laminated iron core, 
from which it is com¬ 
pletely insulated. The 
secondary coil is 
wound around the 
other leg or side of 
the core, from which 
it also is completely 
insulated. In Fig. 197 it is only intended to convey a general 
idea of the relation of coils and core. In actual practice 
the coils are located as close together as they can be 
gotten. In some forms of construction one coil is inside the 
other. 



ELECTRICAL ACTION. —The electrical action of a trans¬ 
former is primarily based on the fact that if a wire be charged 
with alternating electro motive force it will be surrounded 
by a magnetic field, as illustrated in Fig. 198, in which A is a 
wire charged with A. C., B another wire having no mechani¬ 
cal connection with wire A, and the circles lines of magnetic 
force. Under the conditions shown, although wire B has no 
metallic connection with wire A, and is electrically insulated 
therefrom, an alternating current electro motive force will 














MANAGERS AND PROJECTIONISTS 


5'i5 


be induced or generated in wire B, and if wire A and B form 
complete circuits, current will flow in B. 

A transformer depends for its action on this principle, 
supplemented by the following: When the switch is closed, 
charging the primary coil in Fig. 197 with alternating E. M. F., 
the wires thereof instantly become surrounded by lines of 
magnetic force, as shown in Fig. 198, and these lines of force 
acting on the iron core create a magnetic field of great 
intensity. This causes the primary coil to become in effect a 
choke coil of such power that unless current be taken from 
the secondary, and power be thus consumed, no wattage at all 
will be consumed in the primary coil. Electro motive force 
and current is generated in the secondary coil, which is im¬ 
mersed in the magnetic field created by the primary coil, 
because the magnetic field is in 
fact a magnetic circuit, its lines 
of magnetic force flowing in a 
fixed path through the air from 
the north pole to the south pole 
of the field. 

Reverting back to “H o w 
Electricity Is Generated,” Page 
6, we find that electricity is 
generated in the armature of a 
dynamo because the wires cut 
across the lines of magnetic 
force which constitute the mag¬ 
netic field. In a transformer Figure 198. 

the same identical thing is true 

in reverse. Current is generated in the secondary coil by reason 
of the fact that, instead of the wires themselves moving and 
cutting lines of force, the flow of magnetic energy “cuts” or 
passes across the wires, which amounts to exactly the same 
thing as the wires cutting through or across the lines of 
magnetic force, hence a current of electricity, called the 
•secondary current, is generated or “induced” in the secondary 
coil. This secondary current is termed an “induced” current. 

The action of a transformer is entirely automatic. The 
primary current creates a magnetic field which, as already 
explained, generates or “induces” a current in the secondary 
coil. This latter current also sets up a magnetic field, but 
its magnetic flow is in a direction opposite to the flow of the 
primary field. It therefore follows that when the secondary 
current flow is increased or decreased, the relative strength 
of the two magnetic fields (primary and secondary) is 






546 


HANDBOOK OF PROJECTION FOR 


altered, whereupon the amount of current the primary coil 
takes from the lines is automatically increased or decreased 
until just sufficient is taken to maintain the balance between 
the magnetic fields. The action of a transformer, therefore, 
depends upon the balanced magnetizing action of its two 
coils. 

Roughly the foregoing describes the electro-magnetic 
action of all transformers. 

TWO TYPES. —There are two types of transformer, viz.: 
the straight transformer, in which there is no mechanical 
connection between the two coils, and the auto transformer, 
the wiring of which is illustrated in Fig. 199. The auto 



c o 



Figure 199. 


Figure 200. 


transformer is an instrument having but one coil or winding, 
which serves for both the primary and the secondary coil, 
In Fig. 199, L is a laminated iron core on which the primary 
and secondary are wound in the form of one coil, or if you 
prefer it, two coils connected in series so that they prac¬ 
tically form one coil. The primary wires are connected as 
shown, one to the terminal of the primary coil and the 
other to the terminal of the secondary coil at S. The 
secondary wires connect to one terminal of the secondary 
coil at T, and to the other terminal of the secondary coil at 



























MANAGERS AND PROJECTIONISTS 


547 


S, as shown. The ratio of secondary voltage to primary 
voltage will depend upon the ratio of the number of turns 
in the primary as compared to the number of turns in the 
secondary, just as in the ordinary transformer. 

If connection T were made in such way that the number 
of turns in the primary would be two-thirds the total num¬ 
ber of coils in the primary and secondary combined, then 
the secondary voltage would be about one-third the primary 
voltage, and the secondary amperage will be about three 
times that taken from the supply lines. The auto trans¬ 
former may be, and frequently is, so made that the secondary 
terminals may be, by means of proper switches, connected 
to points located anywhere along the length of practically 
the entire winding. There is at least one auto transformer 
which is designed for projection work. It is the product of 
a western coast manufacturer. It is reported as giving 
satisfaction. . 

EFFICIENCY. —Assuming a 100 per cent, efficiency, the 
watts consumed in the primary coil will equal the wattage 
output of the secondary coil. Like all other devices, how¬ 
ever, the transformer is not 100 per cent, efficient, though 
if well designed it should have an efficiency of better than 
90 per cent. The losses in the transformer consist in what 
is known as core and copper losses, the percentage of loss 
depending upon the construction of the device. If a trans¬ 
former which is in good order operates at high temperature, 
it is evidence of lack of efficiency, as core and copper losses 
appear in the form of heat. 

TRANSFORMER CORE. —The core of a transformer con¬ 
sists of thin sheets of sheet-steel, technically known as 
“electrical steel.” The sheets are painted on either side with 
an insulating compound and then clamped together into a 
solid mass. The thickness of the sheets of metal necessary 
for best performance is dependent on the cycle of the cur¬ 
rent the device is to operate on. 

RATIO OF TRANSFORMATION. —A transformer may 
either be a “step up” or a “step down” transformer. A step 
down transformer is one in which the secondary voltage is 
lower than the voltage impressed upon the primary, and the 
amperage correspondingly greater. For instance, if a trans¬ 
former were 100 per cent, efficient and ten amperes at 100 
volts (10 x 100 = 1,000 watts) were taken from the supply 
lines, and in the process of transformation the voltage was 
lowered to 50, then the secondary amperage would be 20, 


548 


HANDBOOK OF PROJECTION FOR 


because 1,000 watts -s- 50 volts = 20 amperes, and with 100 
per cent, efficiency the primary wattage divided by the 
secondary voltage must and would be equal to the secondary 
amperage. This always holds true, subject only to modifica¬ 
tion by the losses inherent in the transformer itself. 

A step up transformer is one in which the voltage induced 
in the secondary is higher than the voltage impressed upon 
the primary, and the amperage correspondingly lower, thus 
reversing the action of the step down transformer. As in 
the case of the step down transformer, however, the wattage 
of the secondary will be equal to the wattage of the primary, 
less the losses inherent in the device itself. 

The ratio of transformation depends upon the relative 
number of turns of wire in the primary and in the secondary. 
If the number of turns in the primary exceed the number of 
turns in the secondary, or in other words if there are a 
greater number of turns of wire in the primary than in the 
secondary coil, the action will be that of a step down trans¬ 
former. In the case of a projection transformer, the voltage 
of the secondary must be just sufficient to force the desired 
number of amperes against the resistance of the secondary 
circuit and the arc. 

This is easily calculated. For example: A transformer 
with 100 turns in its primary and 10 turns in its secondary 
coil, will have a transformation ratio of 10 to 1, and if the 
primary voltage be 100, the secondary voltage, at no load, 
will be 10. If 10 amperes flow in the primary of a trans¬ 
former having a transformation ratio of 10, then 10 x 10 
amperes will flow in the secondary. The whole matter is 
summarized in the following: 

Primary voltage: Secondary voltage = primary turns: 
secondary turns. 

Primary amperes: Secondary amperes = secondary turns: 
primary turns, from which it is evident that, except for losses 
in the device, the wattage of primary and secondary will 
always be equal. 

In examining the step-down transformer it will be found 
that the wires of % the secondary coil are larger than the wire 
of the primary coil. This is because of the fact that the 
secondary amperage will be higher than the primary amper¬ 
age, hence a wire of larger capacity is required. 

The coils are completely insulated electrically from each 
other and form the core, but magnetic lines of force pass 
through insulation just as though it were not there. 


MANAGERS AND PROJECTIONISTS 


549 


RELATIVE POSITION OF THE TWO COILS.— While 

Fig. 197 shows the theoretical construction of the transformer, 
in actual practice the two coils are either wound one over 
the other, or they are placed side by side. In any event they 
are as close together as they can possibly be gotten, in order 
that the secondary coil be located in the strongest part of the 
magnetic field set up by the action of the primary coil and the 
core. 

Broadly, this describes the general plan of construction and 
action of the transformer. Those who wish to delve more 
deeply into the matter of transformer construction and ac¬ 
tion may do so by consulting Hawkins’ Electrical Guide No. 
6, pages 1377 to 1456, wherein will be found a very complete, 
well illustrated description of the construction, the theoretical 
and the practical action of the transformer. 

LOW VOLTAGE TRANSFORMERS.— For use on projec 
tion circuits, where the supply is alternating and it is for any 
reason not deemed expedient to rectify the current by means 
of a motor generator or mercury arc rectifier, there are a 
number of devices which are in fact nothing more or less 
than low voltage transformers. These transformers are made 
especially for use on projection circuits. They pass under 
various trade names. The three best known and most largely 
used are the “Economizer,” which was the invention of J. H. 
Hallberg; the “Inductor,” which is the product of the Nicholas 
Power Company, and the A. C. to A. C. “Compensarc,” w T hich 
is made by the Fort Wayne branch of the General Electric 
Company. They are all of the type known as “constant cur¬ 
rent transformers.” 

These devices take A. C. directly from the supply lines 
and deliver A. C. secondary current at arc voltage. They are 
all so constructed that the amperage of the secondary may 
be altered, usually in three steps, merely by the manipulation 
of a suitable switch connected to taps from the primary 
winding, (see Fig. 200), modified by the fact that in the older 
types of one of them, the economizer, the change in sec¬ 
ondary amperage.is accomplished by means of changing the 
primary connections, either directly or by means of changing 
the position of a plug fuse, instead of by means of a switch. 
They are, of course, all of them step down transformers. 
The maximum capacity of these transformers is 60 amperes, 
but most if not all manufacturers make a special high capacity 
instrument. 

We would suggest to manufacturers of this type of trans- 


550 


HANDBOOK OF PROJECTION FOR 


former that instead of the regular stock transformer having 
a range from 40 or 50 to 60 or 65 amperes, as is the present 
practice, the purpose would be very much better served if 
such devices had a range of from 50 to 80, because 50 is as 
low an alternating current amperage as ought to be used for 
the projection of modern motion pictures, and 80 amperes 
is none too high for good work. 

ADJUSTMENT. —The change of secondary amperage usual¬ 
ly is accomplished by means of “tapping in” on the primary 
coil. This is illustrated in Fig. 200, in which A-B-C are wires 
connecting with the primary coil at various points, and D 
the adjusting switch of the transformer. Remembering that 
the E. M. F. and the amperage of the secondary is dependent 
upon the relative number of turns of wire in the primary and 
scondary, it will readily be understood that the altering of 
the position of switch D would alter the voltage and amperage 
of the secondary, since it would add to or reduce the active 
turns of wire in the primary coil. We believe no further 
explanation of this point is necessary, since the drawings and 
what has already been said, should make the matter suffi¬ 
ciently clear. Change in secondary amperage may also be 
accomplished by altering the position of the primary and 
secondary coils with relation to each other. 

WIRE SIZES. —Where the projection circuit is served by 
an Inductor, Economizer, or Compensarc of 60 amperes 
secondary capacity, the usual custom is to install primary 
circuit wires of only sufficient capacity to carry the primary 
current, which will be decidedly less than the secondary 
current. We would, however, recommend that the primary 
and secondary circuit wires be of equal size, with a capacity 
of, say, 70 amperes, because in case something goes wrong 
with the low voltage transformer it may become necessary 
to temporarily install a rheostat, and if this be done, certainly 
one would not wish to pull less than 60 amperes, under which 
condition the wires of the primary circuit would be too 
small. 

PERMISSIBLE TEMPERATURE.— See Pages 460, 461. 

THE CHOKE COIL. —The choke coil, also called a “react¬ 
ance” coil, is diagrammatically illustrated in Fig. 201. It 
represents what might be called magnetic resistance. If an 
iron core consisting, in practice, of thin sheets of metal, be 
built up, and one of the insulated wires of an alternating 
circuit be wrapped a number of times around it, as shown, 


MANAGERS AND PROJECTIONISTS 


551 



magnetic reactance will be set up, which will have the effect 
of offering resistance to current flow. This is also called 
“magnetic kick.” The magnetic field set up around the core 
of the coil has the effect of creating a counter E. M. F., 

which opposes the line volt¬ 
age and reduces it. The 
practical effect upon current 
flow is essentially the same 
as that of the rheostat, but 
the choke coil is very much 
more economical in opera¬ 
tion than is the rheostat, 
though it is not nearly so 
satisfactory for the produc- 


Figure 201. 

tion of projection light as is 
the transformer or auto 
transformer, or even the 
rheostat, largely by reason 
of the fact that it has a 
tendency to produce flaming 
at the carbons; also pro¬ 
jection light from an arc 
supplied by a choke coil 
usually has a harsh, bluish, 
very unpleasing tone. 

TWO WIRE TO THREE 
WIRE. —Transformers may 
be built to take current from 
a two wire supply and de¬ 
liver to a three-wire system, 
as per Fig. 202. 

MULTIPLE CONNEC¬ 
TION. — Projection trans¬ 
formers of the same voltage 
and cycle rating may be 
connected in multiple in 
order to increase the am¬ 
perage at the arc. To accom- 























552 


HANDBOOK OF PROJECTION FOR 


plish this, connect the two economizers, compensarcs or 
inductors (an economizer and a compensarc, a compensarc 
and inductor or an inductor and economizer may be thus 
connected) to the supply separately, just as though each was 
to work alone, then connect the secondaries as showm in 
Fig. 203. 

Having made this connection, it is permissible to set one 
transformer at its maximum and the other at its minimum 
capacity. By this arrangement a very wide range of current 
flow is available. 

GENERAL ELECTRIC A. C. TO A. C. COMPENSARC.— 

This device is made by the Ft. Wayne branch of the General 



MULTIPLE CONNECTION. SWITCHES AND FUSES 0MITTE2J- 

Figure 203. 

Electric Company. Its general appearance is shown in Fig. 
204. It is entirely self-contained, is well built and delivers 
40, 50 and 60 amperes to the arc. 

CAUTION: Before installing see that the voltage rating 

and cycles on the name plate correspond with that of the 
current supply. 

LOCATION AND CONNECTIONS.— The compensarc 
should be so located that its controlling switch will be within 
easy reach of the projectionist from working position beside 
the projector. Any other location will greatly lessen the value 
of amperage control. 

























MANAGERS AND PROJECTIONISTS 


553 



The connections are shown in Fig. 205. The “line” and 
lamp” terminals are plainly marked on the top of the device, 
so that no mistake is possible in connecting. Connect the 
taps marked line to the supply line, through fuses and 
switch, and the taps marked “lamp” to the projector table 
switch. It makes no difference 
which wire leads to upper or 
lower carbon. 

The compensarc employs the 
means of changing secondary 
amperage illustrated in Fig. 206, 
in which A-B are small reactance 
coils which are cut in or out of 
series with the primary coil by 
means of switch lever, which 
swings to the left, its outer end 
carrying the handle seen on the 
top Fig. 206. Tracing the current, 

Fig. 206, you will see it must 
pass through both coils A and 
B, but with the switch making- 
contact with E, coil B is elim¬ 
inated, and with the switch in 
‘contact with F both coils A and 
B are cut out. 

The claim is that by this plan 
a constant current is secured at 
varying arc voltages. 

To determine whether or not 
all the switch contacts are in 
good condition, start the arc on 
low and then watch the effect 
on the screen illumination as 
you move the switch to in- Figure 204, 

termediate and high. If the 

device is in good order on all steps the effect will be quite 
visible. 


HALLBERG ECONOMIZER.— The Hallberg A. C. to A. C. 
economizer is nothing more or less than a low voltage trans¬ 
former of the semi-constant current type, designed especially 
for use on projection arc circuits. It takes A. C. at line 
voltage and delivers A. C. at arc voltage. “Semi-constant” 
means that, according to its manufacturer’s claim, it will 
receive the supply at fixed potential, but will deliver current 




554 


HANDBOOK OF PROJECTION FOR 


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MANAGERS AND PROJECTIONISTS 


555 


to the arc at practically steady amperage flow, regardless, 
within reasonable limits, of the length of the arc. 

Fig. 207 is the diagrammatic representation of the latest 



type of Hallberg economizer. The two wires marked “to 
lamp” are the terminals of the secondary coil, one of which 
should be connected to the upper and one to the lower 



Figure 206. 









































556 HANDBOOK OF PROJECTION FOR 

carbon of the lamp. It makes no difference which is con¬ 
nected to the upper or lower carbon. 

The primary winding is supplied with three tap connections 
which are attached to the contacts of the dial switch, the 
governor handle of which is seen on top of the economizei. 
The central point connects to one side of the supply circuit. 



The other side of the supply circuit is connected directly to 
the primary coil. A handle with a pointer serves to set the 
dial switch at high, medium or low. 

The old designs of the economizer do not have this switch, 
but instead have three tap leads as per Fig. 208, in which 
terminal 4 represents one end of the primary winding, and 
terminal 1 the other end. A-B-C, Fig. 208, are fuse receptacles, 


























































MANAGERS AND PROJECTIONISTS 557 

and leads 2 and 3 are taps connecting to the primary coil as 
per Fig. 200, page 546. If a fuse plug of sufficient capacity 
to carry the primary current be placed in receptacle C, with 
receptacles A and B empty, then as you will readily see, the 
whole of the primary coil will be in use. This connection is 
designed for use where the primary voltage is a little above 
normal, or when you require the lowest amperage the econo¬ 
mizer will deliver. If the fuses be removed from C and 
placed in A, then a proportion of the primary coil will be 
cut out, which will have the effect of raising E. M. F. of the 



bigure 208. Figure 209. 


secondary voltage, hence the amperage at the arc. The fuse 
plug should be in receptacle A when the voltage is a little 
below normal, or when the highest available amperage is 
wanted at the arc. 

CAUTION.—Do not unscrew fuse plug while the arc is 
burning. If you do an abc will be formed when the fuse 
disconnects from its contact, which will probably result in 
a ruined fuse receptacle. Aside from this the arrangement is 
cheap, practical, and one which should never give trouble. 

Fig. 209 shows the appearance of the latest Hallberg 
economizer. The projector table switch should always be 
on the line or primary side of the economizer. 

POWER’S INDUCTOR.— Power’s Inductor, Fig. 210, con¬ 
sists of a well insulated, strongly clamped laminated core 




558 


HANDBOOK OF PROJECTION FOR 



with the primary wound on one side or leg of the core and 
the secondary on the other. The casing consists of a cast- 
iron front and back, with a perforated fibre cover. On the 
front, at the top, two wires emerge, underneath which, on 
the casting, is the word “lamp.” These two wires connect 
directly to the carbon arms of the projector lamp. It makes 
no difference which wire you connect to the upper or lower 

carbon arm. At the rear side, 
near the top, the two primary 
leads come out. They should 
be connected to the supply, as 
per Fig. 205, Page 555. On 
the face of the front casting is 
a handle which operates a single¬ 
pole knife switch, located on 
the opposite side of the casting. 
When this switch is thrown so 
that its finger points toward 
“high” you are getting the 
maximum amperage, approxi¬ 
mately 65 if the supply voltage 
is 110. When it points to “me¬ 
dium” you are getting a medium 
amperage, and when it points to 
“low” you are getting lowest am¬ 
perage transformer will supply. 

The inductor is designed for a 
maximum of 65 amperes on 
“high,” 54 on “medium,” and 
45 on “low” when used on 110 
or 220 volts, it being, of course, 
understood that you cannot use 
110 volt inductor on 220, or a 
220 on 110. In other words, you must have an inductor suit¬ 
able to the voltage of your supply; also it must be suitable to 
the cycle of the current you use, though the inductor may be 
used on voltage ranging 10 per cent, below to 10 per cent, 
above that for which it is rated, but in one case there will be 
a corresponding increase, and in the other a decrease in its 
rated amperage. The inductor is designed for a maximum 
temperature rise of 50 degrees Fahrenheit above the surround¬ 
ing atmosphere, and ordinarily its temperature will not exceed 
30 degrees in excess of the surrounding air. It occupies 12 x 14 
inches floor space, is 19 inches high, and weighs approximately 
100 lbs. Its efficiency rating will compare favorably with others. 



MANAGERS AND PROJECTIONISTS 


559 


Automatic Arc Controls and 
Mechanical Arc Feeds 

M ODERN projection practice demands the elimination of 
the hand fed projection arc lamp, because the hand fed 
lamp only supplies evenness of screen illumination 
when the feeding of the carbons is given very much closer 
attention than is ordinarily the practice. 

There are now on the market several devices by means of 
which the separation of the carbon points of the arc lamp 
may be either automatically or semi-automatically main¬ 
tained at any desired distance of separation, and while these 
devices cannot be entirely depended upon to maintain exactly 
the desired separation under all conditions, still a well de¬ 
signed arc controller, either of the automatic or mechanical 
feed design, will require but very little attention on the part 
of the projectionist, and if there be no change in amperage 
should maintain the required separation without attention, 
either during an entire show or during the burning away of 
an entire set of carbons. 

AUTOMATIC ARC CONTROLLERS.— The style of ap¬ 
paratus accomplishing automatic regulation of the arc is 
dependent upon the variation in arc voltage for its operation. 
This type of apparatus has an adjustment provided by means 
of which it may be set to automatically maintain any desired 
distance of separation of the carbon points. The mechanism 
is operated by a small motor, and changes in the arc voltage 
are depended upon to alter its speed. A well designed auto¬ 
matic arc control, which is kept in proper condition and ad¬ 
justment, ought to maintain a practically constant separation 
of the carbon points, or in other words a practically non¬ 
variable arc length. 

ARC VOLTAGE. —It may be convenient to users of this 
book if we here briefly explain just what is meant by “change 
in arc voltage,” although that is fully set forth elsewhere, 
see Page 399. When an electric arc is operating, a stream of 
gas, or vapor exists between the carbon tips. This gas or 
vapor is the product of volatilization of carbon. It is a high- 


560 


HANDBOOK OF PROJECTION FOR 


resistance conductor of electricity, and what is known as “arc 
voltage” is the pressure necessary to force the required 
amount of current across the gas stream from one carbon tip 
to the other. The voltage necessary to do this with a given 
distance of carbon separation will vary somewhat, according 
to the kind and amount of gas present, but with any given 
condition as to gas (and the gas condition is constant for any 
given carbon combination, provided the core does not drop 
out, or be missing altogether, or the arc be not exposed to 
excessive draft or sudden current disturbances or varia¬ 
tions) the arc voltage will be directly dependent upon the 
distance between the carbon tips. 

Reduced to simple terms this means that, in practice, every 
change in distance between the carbon tips of an arc alters 
the arc voltage, because it operates to change the resistance 
of the arc. As the distance between the carbon points in¬ 
creases the arc voltage rises, since a higher voltage is neces¬ 
sary to force the current across the wider opening. Con¬ 
versely, as the distance between the carbon tips is decreased 
the arc voltage is reduced. 

MECHANICAL ARC FEED DEVICES.— The purpose of 
these devices is to feed the carbons together at a rate of 
speed exactly equal to the speed with which the carbon is 
consumed. They take their driving power directly, or semi- 
directly from the motor which drives the projector, and if the 
speed of the driving element itself be constant, and the 
rate of consumption of the carbon itself be constant, there is 
no reason why the mechanism cannot be so adjusted that the 
desired separation of the carbon points will be maintained 
at a practically constant value. It is evident, however, that 
any change in the amperage will alter the rate of the speed 
of carbon consumption, and will therefore necessitate a 
change of the rate of feeding. As a matter of fact, however, 
the average projectionist does not often change the amperage, 
and when he does the altering of the speed of feeding is a 
simple matter, and easy of accomplishment. 

It may therefore be said that, always provided the device 
be well designed and well constructed, either the automatic 
arc control or the mechanical arc feed will serve an excellent 
purpose. Each type of apparatus has its advocates. The 
automatic type cannot be used to regulate an A. C. arc. We 
would therefore advise prospective purchasers to examine 
carefully into the relative merits of the automatic and me¬ 
chanical arc feeds, and to decide for themselves which will 


MANAGERS AND PROJECTIONISTS 


561 


best suit their needs. The mechanical arc feed can be used 
for either a D. C. or an A. C. arc. 

WHY CONTROLLERS SHOULD BE USED.— A further 
definite statement of why arc controllers should be used is 
perhaps in order. In the first place, if a -hand-fed arc be 
used, in order to secure maximum results in evenness of screen 
illumination, and maximum returns in screen illumination per 
k. w. of energy expended, it is absolutely essential that the 
projectionist remain constantly beside the projector, feeding 
the carbons a very little at a time, and very frequently—in 
fact, every few seconds. In no other possible way can a 
perfect centering of the spot at the aperture be maintained. 
As a matter of fact not one projectionist in a hundred ful¬ 
fills this condition. This is sometimes due to the fact that 
the multiplicity of duties imposed upon him by the theatre 
management will not admit of his doing it. In other cases 
he does not do it because he is just too careless or too lazy, 



Plate I, Figure 211. 





562 


HANDBOOK OF PROJECTION FOR 


but no matter what the reason may be for such failure, the 
result is bad, and justification of the investment necessary 
for proper arc control is more than ample. 

In considering matters of this kind, the theatre management 
will do well to remember that after it has invested anywhere 
from a few thousand to a half million dollars in a theatre 
building, and has paid large sums for its furnishing in the 
finest possible way, its ventilation in the most complete 
possible manner and its artistic lighting and has paid large 
sums for film service rental, it cannot possibly be good busi¬ 
ness to attempt to save a comparatively small sum of money 
by the investment of which the very heart of everything, the 
projection light source, will not only operate more economi¬ 
cally and efficiently, but also will give a more even, constantly 
brilliant screen illumination. 

We strongly advise all exhibitors using an arc light source 
for projection to install arc controls. 

FULCO SPEEDCO AUTOMATIC ARC CONTROL is the 

re-designed and improved arc control formerly known as the 
Speedco. 

The Fulco Speedco Automatic Arc Control is of the auto¬ 
matic type. It makes use of two basic principles, viz: Me¬ 
chanical and electrical. The device is mechanically well 
made, and the experience of years has proven that it may be 
depended upon to perform the duty for which it is designed. 

By referring to Plate I, you will see that the control 
consists of a small motor, A, directly connected through a 
flexible coupling to the controller mechanism, B. Controller 
B is connected to the arc lamp through the mechanism and 
rods illustrated in Plate II. The general assembly of the 
whole is shown in Plate V. 

The controller is illustrated, in detail, in Plate I, in which 
6 is the fuse box, 5 the snap switch which operates motor 
A, 8 the conduit protecting circuit connecting motor A and 
fuse box 6, 7 the conduit protecting circuit connecting the 
fuse box to the projector table switch, as shown in Plate IV. 
Beside the fuse box, to the left in Plate I, is the disassembled 
assembly illustrated in Plate II, in which 2 is the hand carbon 
feed wheel, 3 the thumb screw which locks the hand control 
to the mechanical control, 12 the gear operating the lamp 
carbon feed rod which is driven by gear 6, Plate II. Rod 2 
and 2A in Plates I and II are the same, they being the rod 
which connects the control to the lamp carbon feed handle. 
This rod is adjustable in length, because rod 2A, which is 


MANAGERS AND PROJECTIONISTS 


563 



square in form, telescopes into a square opening in rod 2. 

Plate III illustrates the mechanism contained in controller 
B, Plate I. In Plate III gear 10 in the left hand illustration 
is the one which meshes with gear 44 in the right hand 
illustration (the right hand illustration being the under side 
of the cover of controller B, Plate I) which latter, through 
bevel gear 50, drives rods 2 and 2A, Plates I and II. 

Now follow closely: 

Spring 41, Plate III, 
is attached to part 23 
by slipping the bend 
in the end of spring 
41 into eye hole 22 of 
part 23. When cover 
40 is in place and ten¬ 
sion is supplied to 
spring 41 by means of 
adjusting dial 20, Plate 
I, which operates on 
threaded bolt 45, Plate 
III, it has the effect 
of holding part 23, 

Plate III, back in the 
direction of arrow 
point 34, Plate III. 

Part 28-28 are gov¬ 
ernor weights attached 
to governor yoke 27 
by means of hinge 
pins 35 and 47, and 
right here is what 
might be termed the 
heart of the whole 
machine. P a r t 33 
swivels on part 32, 
and the whole gov¬ 
ernor is rigidly at¬ 
tached to the main Plate II, Figure 212. 

driving shaft by pin 

38 in part 27. Part 31 is a steel tooth attached to part 23, 
and protruding l /& on an inch on the side next to wheel 16. 
The parts between 27j^, which is a ball-bearing, and part 26, 
which is another ball-bearing, comprise the entire governor 
assembly, which revolves at the speed of the motor armature 
shaft, with which the controller driving shaft is directly 







564 


HANDBOOK OF PROJECTION FOR 


connected, as shown in Plate I. Weights 28-28 are normally 
held in, in the position shown in Plate III, by means of spiral 
spring 41, which holds part 23 back against ball-bearing 26, 
whcih in turn presses back part 32, carrying pins 25 which 
bear on the inner end of arms carrying weights 28-28. Before 
proceeding any further, study this action closely and get the 
action clearly fixed in your mind. 

And now here is how the mechanism operates. The motor 
runs constantly, but at a speed varying with the arc voltage. 



Plate III, Figure 213. 

Its speed increases as the voltage is increased by the increas¬ 
ing length of the arc. As a result of the increased motor 
speed the tendency of weight 28-28 to be carried out by 
centrifugal force, against the pull of spring 41, has the effect 
of overcoming the pull of the spring and forcing part 32, ball¬ 
bearing 26, and part 23 ahead, which causes tooth 31 to 
engage with one of the stop teeth, 15, Plate I, on wheel 16. 

Gears 14, 17 and 29 form what is known as a “differential.” 
Gear 29 is attached to wheel 16, gear 14 to shaft 19 by means 
of pin 13, and gear 17 to gear 18. Underneath gear 18 is a 






MANAGERS AND PROJECTIONISTS 


565 


worm gear attached to the shaft connecting the controller 
to the motor; in other words, to the main driving shaft. 
This worm drives worm gear 18, which is mounted upon, but 
is not attached to shaft 19; in other words, shaft 19 merely 
serves as a spindle upon which gear 18 revolves. When the 
motor is running, but with insufficient speed to cause the 
governor to operate, or in other words when the motor is 
running and the arc not being fed, gear 18 and wheel 16 
are driven continuously. Wheel 16, which is also loose on 
shaft 19, being free to turn, gear 29 simply runs around on 
gear 14, but without revolving gear 14 which is pinned to 
shaft 19, as is also gear 10 which operates gear 44, the latter 
in the right-hand illustration. When the governor operates, 
however, it forces out tooth 31, which engages with one of 
the teeth on wheel 16, thus preventing the wheel from revolv¬ 
ing. whereupon, (remember 
that gear 18 and wheel 16 are 
loose on shaft 19) since gears 
18 and 17 revolve continuously, 
and since gear 29 locks gears 
14 and 17 together when wheel 
16 is not revolving, shaft 19 is 
rotated, together with gear 10 
and gears 44 and 50, and thus 
the carbon feeding mechanism 
is operated, and the carbons 
fed together until the arc 
voltage is sufficiently reduced 
to slow the motor down until 
spring 41 pulls governor weights 
back again, thus releasing 
wheel 16 and unlocking the differential, whereupon the carbon 
feeding mechanism stops. 

All that sounds very complicated, but it really is not. On 
the contrary it is very simple once you get the idea of the 
action of the differential. 

All gearing is fully inclosed, therefore protected from the 
grinding action of dust mixed with lubricant. 

ADJUSTMENT. —The longer the arc the higher its voltage, 
therefore the faster will the motor of the controller run, and 
the speed necessary to cause tooth 31, Plate III, to engage 
with the teeth on wheel 16, Plate I, will depend upon the 
tension given spring 41, Plate I. by adjusting dial on wheel 
20, Plate I, to maintain any desired arc length. 





















o66 


HANDBOOK OF PROJECTION FOR 


SUPPORTING STANDS.— Plate V illustrates different 
types of supporting stands. At the left the controller is 
seen on the floor, in the center raised about six inches, and 
at the right it is raised up about two feet, though the last 
stand can be made up, on special order, to any height required, 
as the supporting column can be made longer. This brings 
the control to any desired height, and so accommodates those 
extreme conditions which are at times met. 

Either type of stand may be had with the outfit at a small 
added cost, remembering that the rod which connects the 
controller with the carbon feed handle is adjustable as to 
length, therefore, the use of the lower stand is optional, but 
the last or higher stand requires a telescoping rod of about 
half the length of those ordinarily supplied. 

We advise the last or higher stand, as this raises the device 
out of the dirt, and looks neater; also it affords a better 
operating position, as it is not necessary to stoop over when 
making an adjustment. The stands are constructed so as 
to catch and hold any oil which may leak from the control¬ 
ler, thus keeping the floor clean and free from oil. 

CONNECTING THE CONTROLLER.— When the controller 

is unpacked, examine the packing material very carefully to 
make sure it contains no small parts. The shipment will 
consist of the following: the controller, motor and base 
connected in one unit, with the necessary switch, fuse box, 
fuses and wire circuits protected by a flexible conduit, steel 
rod and tube, universal joint, fibre knobs and gearing neces¬ 
sary to attach the gear to the carbon feed rod of the arc lamp. 

After unpacking and inspecting the parts, proceed as fol¬ 
lows : First, set the controller and motor A and B, Plate I, 
on the floor immediately beneath the carbon feed handle of 
the arc lamp, though if necessary the controller may be set 
a little to one side, or a little back of the carbon feed handle 
of the arc lamp. This may be necessary in some cases where 
lamp controller ha'ndles interfere with the rods 2 and 2A, 
Plate I, or where the conduits coming up out of the floor 
prevent locating the controller in exactly the desired spot. 
It is, however, desirable that rods 2 and 2A, be as nearly 
perpendicular as possible, because universal joints 13, Plate 
II, will not work properly if rods 2 and 2A are set at too great 
an angle. This idea is illustrated in Plate V. 

Switch box and switch, 5 and 6, Plate T, should be attached 
to the projector table switch casing, either on its under side, 
or to the side of the casing. This may be done by drilling 


MANAGERS AND PROJECTIONISTS 


567 


suitable holes and fastening box 6, Plate I, to the projector 
table switch casing, somewhat after the fashion shown in 
Plate IV, by means of suitable bolts, after which a 13/16 of 
an inch hole must be drilled in the projector table switch box 
cover to receive the BX of circuit 7, Plate I. The only 
electrical connection necessary is to attach terminals 9 of 
circuit 7, Plate I, to the terminals of the projector table 
switch at the end of the switch which will be dead when the 
switch is open. If you attach it to the other end of the 
switch, the motor of the arc control will be subject to high 



Plate V, Figure 215; 

voltage, high enough to cause the carbon feeding mechanism 
to operate, unless switch 5, Plate I, be open. See “Caution,” 
page 569 

Do not attach the controller anywhere else except to the 
binding posts of the projector table switch which will be 
“dead” when the switch is open. 

LUBRICATION— The well formed by gear casing B, Plate 
I, shown with cover removed in Plate III, should be kept 
filled to the top of oil gauge 14, Plate I, using a good grade 
of dynamo oil. The oil is put in by removing thumb screw 
19, Plate I, and the filling is continued until the oil reaches 
the top of oil gauge 14, Plate I. One filling of good lubricant 




568 


HANDBOOK OF PROJECTION FOR 


should last about 500 hours, or in a house running 10 hours 
a day for about two months. 

About twice a year the oil well should be drained. After 
draining fill the oil well with kerosene and let the controller 
run for a short time, after which drain the kerosene out and 
re-fill the well with fresh oil. 

CAUTION.—You are cautioned against using Three-in-One, 
and other very thin much advertised oils, as they are totally 
unfit for the lubrication of a device of this kind. 

The manufacturers recommend any good grade of dynamo 
oil, which can be obtained from your supply dealer, or from 
any reliable oil dealer. The oil sold by projector manufac¬ 
turers for use on their projectors will serve very well. 

OPERATION.— The controller will maintain the length of 
arc for which it is adjusted, and the length of arc it will 
maintain may be altered by turning adjustment dial 20, Plate 
I. in the direction as indicated to maintain a longer or shorter 
arc. 

The voltage of your supply lines may change during the 
day, and repeat these changes day after day. Arc controller 
adjusting dial has its face laid off in numbered divisions, and 
there is a pointer, so that by making a note, or by taking 
a record of its operation as the dial is set at different figures, 
the controller can be re-set at those times when the current 
changes take place, without the necessity of making the daily 
experiment of adjusting a thumb screw or nut so as to 
maintain the desired arc condition. If the projection room 
is equipped with a reliable voltmeter it only requires a little 
observation to know exactly where to shift the speed con¬ 
troller dial to obtain the desired results from any given 
voltage. 

CARE.— Examine the oil cups of the motor once a week 
and keep them filled with oil; also examine the commutator 
of the motor occasionally. In this connection see general 
instruction No. 7, Page 509, on care of the commutator. 
Should everything go wrong with the interior gearing of 
the control (very unlikely, though all things are possible) it 
will be necessary to return the entire mechanism to the 
factory for adjustment. It is not advisable that the pro¬ 
jectionist himself attempt to repair the control mechanism. 
The explanation of the mechanism is not given with the 
idea of enabling him to repair it, but because we believe any 
man can work more intelligently with a thing if he under- 


MANAGERS AND- PROJECTIONISTS 


569 


stands its operating principle; also because the average man 
very naturally does not like to operate something he knows 
nothing about. We, therefore, provide him a better means 
of getting the knowledge he desires than by tearing the 
machine to pieces. 

CAUTION.—The controller must under no circumstances 
be connected to alternating current, or to any voltage higher 
than 115. Always place snap switch 5, Plate 1, in the “open” 
position after extinguishing the arc. 

When it is desired to resume operation, first strike the arc 
by hand and set it to approximately proper length, after 
which turn snap switch 5, Plate I, in the “on” position. This 
latter is important, because if the projector table switch be 
closed when the arc is not in operation, as is not infre¬ 
quently the case, the controller motor would be subject to 
voltage sufficient to place the carbon feeding mechanism in 
operation; also, if current be taken from 110 volt direct 
current lines through a rheostat, the motor would he 
operating at line voltage, because with such a very small 
current flow, the rheostat would not operate. 

HALLBERG CONTINUOUS FEED ARC CONTROL.— 

The Hallberg Continuous Feed Arc Control is of the auto¬ 
matic variety. Its operating theory is to a certain extent 
unique, and could not, it seems to us, be very largely im¬ 
proved upon. 

In Fig. 216 the operating mechanism is shown. The prin¬ 
ciple of operation is as follows: In Fig. 216, 3 is a motor, to 
the upper end of the armature shaft of which driving worm 
gear 4 is rigidly attached. Worm gear 4 meshes with gear 
10, through the train consisting of gears 5, 6, 8 and a gear 
on the right-hand end of shaft 9, which engages with gear 10. 
Arc lamp feed control rod 11 acts as a shaft for gear 10, and 
the gear and shaft may revolve independent of each other, 
or they may be locked together as follows: Knurled knob 13 
operates what amounts to a brake shoe on the opposite, or 
back, side of the hub of fiber disc 12. When knurled knob 13 
is slacked ofif, the carbons may be fed in the usual way by 
turning disc 12, but when knurled knob 13 is tightened up, 
feed rod 11 is locked rigidly to motor 3, through the gear 
train already described. 

To strike an arc, the projectionist loosens knurled knob 13 
by about one-half turn, which releases the gear train and 
motor. He then strikes the arc by hand, in the usual way, 
and adjusts it to approximately correct projecting conditions. 


570 


HANDBOOK OF PROJECTION FOR 


He then, in order to remove all possible lost motion in rod 
11 and its connections, turns disc 12 slightly in the direction 
of feeding, and locks it to the gear train by means of knurled 
knob 13. 

Under this condition motor 3 feeds the carbons together 
constantly and at a constant rate of speed. The projectionist 
must then adjust th‘e speed of motor 3 by means of thumb 
screw 14. Part 17 is a coil of fine resistance wire, a part of 
which is in series with both the armature and field of 
motor 3. The connection is as follows: Wire 18 connects 
directly with the motor field and armature, and with the top 
end of resistance coil 17. Block 15 is moved up or down by 
means of thumb screw 14, riding on brass bar 17, with which 
its metal part makes electrical contact. On the back of part 
15 a spring clip is carried which makes sliding contact with 
the raw wire of coil 17. 

Having struck an arc and adjusted it to normal projecting 
as block 15 is lowered by rotating screw 14 in a clockwise 



Figure 216. 














MANAGERS AND PROJECTIONISTS 


571 


direction, a greater amount of the resistance of coil 17 is 
brought into action, and since this resistance is in series 
with the field and armature of motor 3, the speed of motor 3 
is reduced. Conversely, as screw 14 is revolved counter¬ 
clockwise, block 15 is raised, and the speed of motor 3 !s 
increased. 

Having struck an arc and adjusted it to normal projecting 
conditions, the projectionist next proceeds to regulate the 
speed of motor 3, by means of screw 14, until the carbons are 
fed at a speed just a very little less than is necessary to 
maintain the normal carbon separation. In other words, 
speed of motor 3 must be so adjusted that the carbon sepa¬ 
ration will increase very slowly as the arc burns. 

THE AUTOMATIC END OF IT.— Motor 19, which is also 
a series motor, and identical in every way with motor 3, 
has, mounted on the upper end of its armature shaft, a 
governor very similar to an ordinary engine governor. This 
governor is rigidly attached to the armature shaft, and must 
rotate therewith. When the speed of the motor increases 
sufficiently, weights 23 are thrown outward by centrifugal 
force, thus raising part 22 against the pressure of coil 
spring 24. 

Part 26 is a fiber cap attached to a steel spindle, which 
latter passes down through the center of the upper end ol' 
the governor center shaft, and is attached rigidly to part 26 
by means of a screw in the face of part 22. The effect of 
this is, when part 22 is raised by the action of arm 23, part 
26 is lifted vertically. Parts 27 are contact points, normally 
held slightly separated by spring action. When part 26 is 
raised by the governor, these contact points are forced to¬ 
gether, which short-circuits the resistance of coil 17, thus 
increasing the speed of motor 3 and feeding the carbons 
faster, until such time as normal arc length is re-established, 
whereupon, the voltage being reduced to normal, the speed 
of motor 19 drops, the governor resumes its normal position, 
contact points 27 are separated and the resistance of coil 17 
is reinstated in series with motor 3, thus reducing its speed 
to normal. This action all takes place at a very slight 
change in arc voltage—so slight that the change in carbon 
point separation is negligible. 

Knurled knob screw 37 controls resistance coil 40, which 
is in series with the field and armature of motor 19. It 
operates precisely the same as does the mechanism con¬ 
trolled by screw 14, which we have already described. Re- 


572 


HANDBOOK OF PROJECTION FOR 


sistance 40 is used for the purpose of establishing the point 
at which governor 21 will be brought into action. In other 
words, the projectionist may establish his arc length at 
whatever is the best projecting condition, then by the ad¬ 
justment of screw 37 cause governor 21 to come into action 
at the proper time to maintain that arc length within the 
limits of a negligible fraction. 

Twenty-eight is a static condenser coil. It is non-ad- 
justable. Its only purpose is to minimize arcing at contacts 
27, with which it is connected in multiple. 

MOUNTING. —It is neither necessary or advisable to con¬ 
sume valuable space in the giving of detailed instructions for 
mounting, because complete installation instructions accom¬ 
pany each device. 

In the Simplex type S a slide is provided, which takes the 
place of the removable slide in the rear of the lamphouse. 

LUBRICATION. —Motors 3 and 19 are equipped with 
bearings which are presumed to require no oil. It will, 
nevertheless, be advisable to, say once in two weeks where 
it is an all-day house, or once a month for evening shows, 
to put one drop of mechanism oil in the armature shaft of 
motor 19, just where it enters nut 20, and one drop at a 
similar point on the armature shaft of motor 3. Also in 
upper and lower bearing for worn gear, as these are the only 
high speed parts of the controller. 

CAUTION.—ONE DROP we said, mind you! Don’t put 
more on unless you are looking for trouble. Use the same 
oil you use for the projector mechanism. DO NOT LUBRI¬ 
CATE THE GOVERNOR, OR ANY OF ITS PARTS. 

About once a month remove the mechanism cover by 
taking out the four screws holding it, and put a little auto¬ 
mobile grease on the face of the various gears. Don’t smear 
on a lot of grease! Use a little judgment and common 
sense! If you use too much grease, particularly on gears 4 
and 5, look out for trouble. Before putting on fresh grease, 
remove all the old, wiping the gears off clean. This will 
greatly decrease the wear on the gears. 

Gears 5, 6, 8 and the one on the right-hand end of shaft 9, 
may be removed by taking out screws 44 and 45. It is not, 
however, recommended that the replacement of these gears 
be undertaken by the projectionist. . They should, and if 
properly lubricated will, wear until the whole device would 


MANAGERS AND PROJECTIONISTS 


573 


naturally require a general overhauling, at which time the 
controller should be sent to the factory. 

If properly cared for we see no reason why a general over¬ 
hauling should be required in anything less than a three 
thousand or four thousand hour run—perhaps even a great 
deal longer. 

Should anything go wrong with coil 40 or 17, they may be 
replaced by the projectionist by removing screw 31, loosen¬ 
ing the screw at the top of clamp 29 and slipping out con¬ 
denser 28. Next remove screws 46 (two of them) on top of 
the casing, whereupon the parts carying the resistance spools 
may be pulled ahead, and the spools will be released by re¬ 
moving the necessary two screws at the top and at the 
bottom. A new coil may then be slipped into place. 

CAUTION. —In removing and replacing resistance coils be 
very careful to first thoroughly examine and understand 
everything so you can get the parts back where they belong. 

CAP SCREWS. —The motor armature brushes must be ex¬ 
amined occasionally and replaced with new ones when they 
wear out. If dirt and oil accumulate the result may be that 
the brush will stick in the guide tube or fail to make perfect 
contact. For these reasons the brushes must be examined 
now and then and also to make sure that they are not 
worn too short, because if these defects exist the motor 
will not start and will fail to feed the carbons. Remove the 
cap screws and carefully pull out the coil springs . and 
brushes. In replacing be very sure that the brush slides 
freely in the guide tube and that the springs fit with secure 
contact on round part of square carbon brushes. Do not 
bend or stretch the brush springs! Do not fail to replace a 
used brush in such a manner that the concavely worn part 
fits the commutator in order to insure perfect contact. 

PEERLESS AUTOMATIC ARC CONTROL.— The Peer¬ 
less Arc Control is of the automatic type, and is by far the 
simplest, both in mechanical and electrical construction, we 
have yet seen. 

It consists essentially of a small motor, Q, Fig. 217, which 
drives gear T by means of worm gear S, the latter attached 
to the armature shaft. Gear T is attached to and drives 
upright rod B, into which square rod G telescopes. This 
latter is to accommodate varying heights, or in other words, 
to cause the length of combined rods B and G to be ad¬ 
justable. Rod G, through another pair of worm gears, drives 
carbon feed rod P. 


574 


HANDBOOK OF PROJECTION FOR 


When the carbons are not being fed, motor Q and the 
mechanism stands still. The running of motor Q, and 
therefore the feeding of the carbons, is actuated by means 
of a circuit passing from the motor to snap switch K, 
through the box to which conduit O is attached. The cir¬ 
cuit contained in conduit O passes down through the ap¬ 
paratus contained in the box, and on through underneath 
the supporting stand to the motor. 

The control may be used on any make of projector. It is 
designed to stand on the floor, as nearly as possible im¬ 
mediately under the arc lamp carbon feed handle, the com¬ 
plete assembly being illustrated in the diagram shown in 
Fig. 217, in which square rod G telescopes into a square 
opening in rod B, which makes the length of the combined 



Figure 217. 



















































MANAGERS AND PROJECTIONISTS 


575 


rods adjustable to suit varying heights of the carbon feed 
rod from the floor. 

The actuating element is completely inclosed and is sealed. 
When the machine is received you will find attached to one 
of the seals a printed warning that if the seal is broken the 
guarantee on the machine is voided. 

For the benefit of the projectionist, who naturally dislikes 
handling something that he does not understand, we will say 
that there is no reason for breaking the seal, because the 
only thing inside of the sealed box is a relay exactly simi¬ 
lar to the relay in telegraphic instruments, and a small, high 
resistance unit. The operation of the controller is governed 
by changes in arc voltage. Inside the sealed box are two 
highly sensitive magnets, in series with each other, which 
are connected directly across the line in multiple with the 
projection arc. The strength of these magnets will, there¬ 
fore, of course change with each variation in arc voltage. 
At the end of the magnets is an armature attached to an 
upright, the upper end of which is arranged precisely the 
same as the “sounder” of a telegraph instrument, except 
that on one side is a fibre insulator. 

This bar is normally kept pulled away from the magnet by 
the tension of a coil spring attached to adjusting screw A, 
Fig. 217, and when in this position, it rests against the 
insulator. When, however, the magnet pulls the bar over 
toward it, its upper end makes metallic contact which com¬ 
pletes motor circuit CD, Fig. 217, and starts the motor 
running. It works thus: the stronger the tension on the 
spring attached to adjusting handle A, the greater the force 
the magnets will be obliged to exert in order to pull it over 
and complete circuit CD, or, in other words, start motor Q 
running. Suppose when the arc is adjusted to the best pos¬ 
sible condition, the voltage is 55. We then turn adjusting 
screw A, Fig. 217, until motor Q stops just at the point 
where the arc is the way we want it. We will then readily 
understand that under this adjustment, as soon as the carbon 
is consumed and the arc voltage increased, the increased 
strength of the magnets will pull the armature over, com¬ 
plete circuit CD, and start motor Q running, thus feeding the 
carbons together, which process will continue until the arc 
voltage has dropped to normal, whereupon the spring will 
overcome the pull of the magnets, and circuit CD- will be 

broken. . . 

That is the way the Peerless works. It is simplicity itself, 


576 


HANDBOOK OF PROJECTION FOR 


and the device has given general satisfaction. The move¬ 
ment of the armature at its upper end, where the contact 
is made, is only .006 of an inch. 

The projectionist may adjust the controller to maintain 
any desired arc length. The manufacturers claim the sensi¬ 
tiveness to be such that the actuating element will act on 
less than 1/5 of a volt change. We cannot vouch for this, 
but a change of as much as one volt will not materially affect 
the position of the spot at the aperture, hence will not 
affect results on the screen. 

The gear reduction is such that the motor armature must 
make 6,400 revolutions to one revolution of the carbon feed 
handle. Inside the sealed box is also a high resistance unit, 
connected in series with motor Q, Fig. 217. This permits 
some current to enter the motor at all times when the table 
switch of the projector is closed, which serves the purpose 
of reducing to a minimum the load which the circuit breaker 
has to break, thus eliminating any destructive spark. The 
actuating element is guaranteed indefinitely by the manu¬ 
facturers, so long as the seals are not broken. All other 
parts of the instrument are guaranteed against defective 
material or workmanship for a period of one year from 
date of sale. 

WARNING.—The manufacturers report an inclination on 
the part of the projectionists to break the seals and attempt 
to improve the adjustment of the relay points. You are 
warned against doing this, because you cannot improve the 
factory adjustment, and it is not at all likely that this 
adjustment will in any way be disturbed by an extended 
period of operation. 

The gap must be from .005 to .006 of an inch. Anything 
more than that will cause the controller to be coarse in its 
operation. The best thing you can do is to let those points 
alone, but if you feel the voiding of the guarantee is not 
too much of a price to pay for looking at a very simple 
mechanism, and you do break the seals, then by all means 
confine your efforts to looking; but if you feel it is abso¬ 
lutely necessary to tinker with the relay, then secure a 
spacing gauge .005 or .006 of an inch thick, and be sure you 
leave the relay with exactly that gap. 

The Peerless Arc Control can only be used where direct 
current is employed at the arc. It must be so connected that 
circuit CD will receive arc voltage only, which means that 
the connection must be made on the projection lamp side of 


MANAGERS AND PROJECTIONISTS 577 

the rheostat, motor generator, or the mercury arc rectifier. 
It should, in fact, be made to the end of the projector table 
switch which is dead when the switch is open. 

With the Power’s, the Motiograph, or the type S Simplex, 
you disconnect the entire feed handle and rod from the lamp, 
and in its place attach the assembly sent with the con¬ 
troller. With the regular type S lamp, which has the carbon 
feed rod rigidly attached to the lamp, it is only necessary to 
remove the fibre handle and in its place attach the special 
feed assembly supplied for that type of lamp. Rod G is then 
slipped into rod B and the lower end of rod B is attached 



Figure 218. 









578 


HANDBOOK OF PROJECTION FOR 


to the universal joint E, as shown in Fig. 217. Supporting 
rod F may be either attached to one of the lamp adjustment 
handles by means of clips supplied with the outfit, or you 
can drill a small hole in the rear lamphouse wall about five 
inches below the opening through which rod P passes. 

Circuit CD is controlled by snap switch K. The controller 
may be purchased either with box L and snap switch K or 
without. Box L contains a fuse box and two plug fuses 
which protect the circuit. Snap switch K is on the outer 
wall of the box. If fuse box L is purchased, then circuit CD 
will be inclosed in flexible Greenfield conduit O. If box L 
is not purchased with the outfit, then it will be necessary to 
install a plug fuse box and a snap switch. Box L, or the 
fuse block, may be installed anywhere desired, but the best 
and most convenient way is to drill a hole large enough to 
admit the J4 inch chase nipple which projects through the 
back of the fuse box, the nut upon which will hold the fuse 
box in place, through the side of projector table switch box 
R, Fig. 217, and attach the box L on the fuse block thereto 
by means of suitable bolts. If box L is not purchased, then 
circuit CD should be inclosed in flexible conduit between 
the controller and the fuse block. 

From box L on the fuse block, the circuit CD must con¬ 
nect to the binding post of the projector table switch, which 
will be dead when the switch is open. Before installing a 
new trim of carbons, placing snap switch K at “open” put 
in the carbons and let them burn in before closing snap 
switch K. This is advisable because the voltage at the arc 
is much lower while the carbons are burning in than it is 
afterwards. Fig. 218 illustrates the method of installation. 

LUBRICATION. —Once a week slightly lubricate the gears 
with a good grade of automobile grease and at the same 
time oil the bearings and motor. 

TEPECO MECHANICAL ARC FEED.— The Tepeco Me¬ 
chanical Arc Feed consists of a very simple mechanism in¬ 
closed in a pressed steel case, taking its power from the 
motor which drives the projector. 

With the Power’s projector it is connected directly with 
a spindle of the speed control, which in turn connects 
to the motor armature, Fig. 219, so that the speed of driving 
is constant, regardless of the speed of the projector mechan¬ 
ism itself. A special coupler is provided for the purpose of 
making the connection; also a special spindle, which is a 
little longer than the Power’s spindle. It is only necessary 


MANAGERS AND PROJECTIONISTS 579 

to slip out the Power’s spindle and replace it with the 
special. The operation is not at all difficult. The mechanism 
is then connected with the carbon feed handle of the arc 
lamp with a flexible cable and a suitable mechanism. 

A general view of the Power’s installation is shown in 
Fig. 219. 

When attached to the Simplex, the Tepeco is driven by- 
means of a belt which connects a pulley on the side of the 
Tepeco mechanism to the motor which drives the projector. 



Figure 219. 

A general view of the Tepeco attached to a Simplex is had 
in Fig. 220. 

The Tepeco mechanism is connected with the carbon feed 
handle of the arc lamp by means of a flexible driving shaft 
inclosed in a suitable flexible mechanism. 

On the end of the Tepeco mechanism casing is an adjust¬ 
ment thumb screw by means of which the speed of feeding 
may be either increased or decreased. On its face is a 
double pointed arrow. To increase the speed of feeding 
turn the thumb screw in the direction of arrow F, and in 
the opposite direction to decrease the speed of feeding. 

The cover of the mechanism is merely pressed on. It is 
not held by screws and may be removed by inserting the 








580 


HANDBOOK OF PROJECTION FOR 


point of a screw driver in the slot at either end of the casing 
and prying it off. 


MOTIOGRAPH MECHANICAL ARC CONTROL. _The 

Enterprise Optical Mfg. Company, manufacturers of the 
Motiograph projector, make and market a device known as 
an adjustable mechanical arc controller. It, together with 
the Motiograph lamp, is shown in Fig. 220-A. The following 



LUBRICATION. —A drop of the same oil that is used for 
the projector mechanism should be placed in the oil hole on 
the top of the Tepeco mechanism casing once a day, or twice 
a day if it is in an all-day house. The worm gear inside the 
casing should be kept lubricated with automobile or motor 
generator cup grease. Also a drop of oil should be placed 

on the two spindles 
the ends of which 
will be seen when 
the casing of the 
mechanism is re¬ 
moved, also on the 
spindle which pro¬ 
trudes through the 
casing on the back 
side. There is, how¬ 
ever, no necessity 
for oiling these 
more than once a 
week. 

NOTE. —Do not 
put any oil or 
grease on the big 
flat disc, the sur¬ 
face of which looks 
something like the 
face of a file. 

Full instructions 
accompany each 
instrument, and the 
matter of installa¬ 
tion is sufficiently 
simple that any 
projectionist should 

be able to attach the device to his projector. The device has 
been tried out very thoroughly and reports show it to be 
quite satisfactory. 


Figure 220. 








MANAGERS AND PROJECTIONISTS 581 


description will give you a working idea of the construction 
and operating principle of the device. 

The motor, AF-1, Fig. 220-A, is mounted upon a bracket, 
which same is attached to the under side of the lamphouse, 
so that the entire device, motor and all, is readily accessible; 



also it is located well up out of the dust and dirt. On the 
motor armature shaft is a “worm,” which same engages with 
a worm wheel attached to the outer end of shaft carrying 
friction disc AF-5. Friction disc AF-5 engages friction discs 
AF-15 and 16, and when so engaged the two latter discs are 
revolved. The supporting bearings for the shaft carrying 
friction disc AF-5 are a part of the bracket supporting the 
motor. 

Friction discs AF-15 and 16 are mounted on carriage AF-14, 
the rear of which is supported on shaft AF-40; the front end 
is supported by rear end of shaft AF-61 by means of a tongue 
and groove connection. 

Friction discs AF-15 and 16 are held together by the 
pressure of a spring. On one end of the shaft carrying these 









582 


HANDBOOK OF PROJECTION FOR 


discs is a worm, which engages with a worm wheel on lower 
end of vertical shaft AF-27, which same connects to telescopic 
shaft AF-45, and by suitable means, with the carbon feed 
screw AL-225. 

When shaft AF-40 is rotated it moves carriage AF-14, 
carrying friction discs AF-15 and 16 so that friction disc AF-5 
is thrust further between or withdrawn from between fric¬ 
tion discs AF-15 and 16. Since friction disc AF-5 is driven at 
constant speed by the motor it will be seen that rotating 
shaft AF-40 will have the practical effect of increasing or 
decreasing the speed of rotation of friction discs AF-15 and 
16, hence the speed of feeding the carbons. The pro¬ 
jectionist may therefore adjust the speed of carbon feeding 
at will, merely by rotating the knob on shaft AF-40. 

In considering this it must be remembered that the worm 
gears, of which there are two sets between the motor and 
the carbon feed screw AL-225, act to hugely reduce the speed, 
so that a very fine adjustment of actual carbon feeding 
speed is possible. 

While the makers of this and other mechanical arc con¬ 
trols claim it is possible to run a whole trim of carbons 
without any attention on the part of the projectionist, it is a 
question if this is entirely practical. However, in any event, 
any adjustment that may be necessary will be very slight, 
provided the projectionist uses ordinary care in adjusting the 
speed of feeding, and the possible necessary adjustment by 
hand we do not regard as in any way objectionable. 

SIMPLEX MECHANICAL ARC CONTROL.— The Pre¬ 
cision Machine Company, manufacturers of the Simplex pro¬ 
jectors, have evolved a most excellent mechanical arc con¬ 
trol, a description of which follows: 

The control mechanism consists of a speed changing gear, 
mounted on spindle, A, Fig. 221. The control mechanism is 
so mounted that it may be moved sidewise with reference to 
electric motor B, Fig. 221. This feature will be described in 
detail further on. The speed-changing gear is driven differ¬ 
entially by the motor, through a train of three pulleys, one 
of which, C, Fig. 221, is mounted on the motor armature 
shafts, and drives both the projector mechanism and the 
arc control. The other two, D and E, are mounted on the 
spindles which carry the gears of the controller. Pulleys 
D and E are conical pulleys. They are driven from pulley C, 
Fig. 221, by means of a single half-inch flat, rawhide belt, as 
shown. This belt is kept permanently in line with the motor 


MANAGERS AND PROJECTIONISTS 


583 


pulley by means of pulleys 1 and 2, Fig. 221, the upper one of 
which is mounted on adjustable tension lever 3, Fig. 221, so 
that more or less tension may be given the belt. 

The central shaft of the controller, 4, Fig. 221, is con¬ 
nected through a square-shaft telescope, 5, Fig. 223, a flexible 
shaft, 6, Fig. 223, reducing gear, 7, Fig. 223, and a spring 
clutch, 8, Fig. 223, to the arc lamp feed handle, 9, Fig. 223. 
The gear casing of the control is carried on two rods, 10 and 

11, Fig. 222. These rod's are supported by the main frame, 

12, Fig. 222, which carries the whole mechanism of the 
control, including the motor, which latter not only pulls the 
controller, but the projector mechanism as well. 



Figure 221. 











584 


HANDBOOK OF PROJECTION FOR 


Rod 11 uses main casting 12 merely as a journal. In other 
words, it revolves therein, and is held from moving end¬ 
wise by means of collars 13 and 14, Fig. 222. The left-hand 
end of rod 11 is threaded, and these threads engage with 
similar threads in lug 15, Fig. 222, so that when hand wheels 
16-16 are revolved by the projectionist, the whole gear casing 
and cone pulleys D, E, Fig. 221, are moved sidewise, and 
since the motor remains stationary and the controller driv¬ 
ing belt is held stationary by means of pulleys 1 and 2, Fig. 
221, the altering of the position of the gear casing alters the 
position of the belt on pulleys D, E, Fig. 221. 

It will thus be seen that by revolving hand wheels 16-16, 
Fig. 222, the relative speed of pulleys D, E, Fig. 221, with 
relation to each other is altered. 



Figure 222. 










MANAGERS AND PROJECTIONISTS 


585 


Conical pulleys D, E are the driving elements of the 
differential, and the differential drives central shaft 4, Fig. 
221, which connects, through flexible shaft 6, Fig. 223, with 
the arc lamp. 

It is very difficult to explain the action of the differentia^ 
but when the driving belt is in central position pulleys D, E 
will run at exactly the same speed and under that condition 
shaft 4 , Fig. 221, and shaft 5, Fig. 223, will remain stationary. 
If the position of the belt be altered so that pulley D runs 
faster than pulley E, then shaft 4 will be revolved in a 



Figure 223. 























586 


HANDBOOK OF PROJECTION FOR 


direction that will feed the carbons together, and the 
greater the difference in the speed of the two pulleys, the 
faster the carbons will be fed. If, on the other hand, the 
belt be shifted so that pulley E runs faster than pulley D, 
then shaft 4 will revolve in a direction which will pull the 
carbons apart. 

It therefore follows that by revolving knob 16-16, the pro¬ 
jectionist may alter the speed of the feeding of the carbons, 
or may even reverse the action so that the carbons will be 
pulled further apart. The slope or inclination of pulleys 
D, E, Fig. 221, is such that an even tension on the belt is 
maintained throughout the whole range of adjustment, which 
is about one inch. 

Spring clutch 8, Fig. 223, provides a frictional connection 
between the control mechanism and the carbon feed handle 
of the arc lamp. This provides means for adjusting the arc 
independently of the control, or, in other words, by hand, 
which same may be done without disconnecting the control 
from the carbon feed handle. 

The projectionist may strike the arc and adjust the car¬ 
bons to their proper position without in any way interfering 
with the operation of the control. 

The rate of carbon consumption and the necessary rate of 
feeding for any given carbon size and current may be de¬ 
termined by experiment, and once the rate is determined and 
the control set for that rate, very little further attention is 
required unless the amperage be changed. But even, though, 
for any reason the rate of carbon consumption be changed, 
or the speed of the driving motor be changed, the necessary 
readjustment of the control is simply made and easily ac¬ 
complished. 

The control is ruggedly constructed, made of good ma¬ 
terials, and it is mechanically very well made indeed. The 
feeding is entirely mechanical, no electrical devices being 
employed. We recommend the Simplex Mechanical Arc 
Control to the consideration of our readers. It has the 
approval of the projection department of Moving Picture 
World. 

SIMPLEX HIGH INTENSITY ARC LAMP.— The Precision 
Machine Company, Inc., manufacturers of the Simplex Pro¬ 
jector is putting out a mechanically fed and operated high 
intensity arc lamp. One of the main and unusual features is 
that it is available for use at any amperage from 70 to 120. 


MANAGERS AND PROJECTIONISTS 587 

Fig. 223-A is a general view of the operating side of the 
lamp. The positive carbon is shoved through a hole in the 
center of gear 1 and through loose washer 2. In this washer 
is a broad headed set-screw, the tightening of which clamps 
the washer to the carbon so that, as positive carbon carrier 
3 is carried forward by feed screw 4,' the positive carbon is 
also carried forward. 



Figure 223-A. 


Fig. 223-B is an illustration showing the view of the posi¬ 
tive head through which the tip of the positive carbon 5 
protrudes. Current carrying contact with the positive carbon 
is made through positive head 6 and contact tension “brush” 
7. Contact tension brush 7 is pressed down on the carbon 
by finger clamp 8, which is held down by means of spring 9 
Fig. 223-A. 

This is a most excellent arrangement, in that it enables the 
projectionist to almost instantly remove contact tension brush 
7 and thoroughly clean the contact surface. The importance 
of this is understood when we consider that good electrical 
contact can only be had between the carbon and the metal 
when the metal is perfectly clean. 

To remove positive head 10, Fig. 223-A, it is only necessary 
to remove screw 11, Fig. 223-A. Positive head 10 rests in a 
cradle which allows the head to “float.” This is important in 
that it enables the contact to adapt itself to any inaccuracy 










588 


HANDBOOK OF PROJECTION FOR 


either in the circumference or in the straightness of the 
positive carbon, thus preventing tendency to arcing between 
the carbon and the metal. 

The positive carbon has two movements. It is fed forward 
and is revolved. The latter motion is accomplished as fol¬ 
lows : Shaft 12 connects to the mechanical arc control illus¬ 
trated in Fig. 221, and described in the text Page 582. Shaft 
12 revolves shaft 13 through the pair of bevel gears seen at 
14, Fig. 223-A. This in turn drives gear 15 which in its turn 
drives gear 1, thus revolving the positive carbon. 

The positive carbon is fed forward by means of a pin cam 
attached to shaft 13. This cam carries two pins which engage 
with and rotate star wheel 16. 

Star wheel 16 is not attached rigidly to feed screw 4, but 
rides loosely thereon. It is clamped between shoulder 19 and 
a washer on the other side, by means of spring 17, the pres- 



Figure 223-B, 











MANAGERS AND PROJECTIONISTS 589 

sure of which is controlled by knurled thumb screw 18. 
Shoulder 19 is rigidly attached to feed screw 4. With this in 
mind you will readily understand that with spring 17 under 
sufficient pressure the rotating of star wheel 16 will also 
rotate feed screw 4 by reason of the friction between shoulder 
19 and star wheel 16. This arrangement, which is nothing 
more or less than a friction clutch, enables the projectionist 
to rotate feed screw 4 by hand, and thus at any time feed 
the positive carbon independent of the carbon arc control. 
The arrangement is practical and excellent, though the hand- 
feed will of course work stiff since sufficient force must be 
exerted to overcome the friction of the clutch. 

The negative carbon is held by clamp 20, which is tightened 
or loosened by means of set screw 21. This clamp is hinged 
at 23, the carrying lug of which, 26, rides on rods (two of 
them) 25. Spring 24 performs the office of pulling the entire 
clamp assemblage downward, thus causing the tip of the 
negative carbon to rest upon contact cooling plate guide 22 
with considerable pressure. Current is carried to the nega¬ 
tive carbon through conductor 27, which joins clamp 20, as 
shown. Copper strip 28 carries current to contact cooling 
plate guide so that the negative carbon actually receives 
current both through clamp 20 and guide 22. 

The negative carbon is fed upward by means of feed screw 
29, which is rotated by means of star wheel 30. The action is 
exactly similar to that of star wheel 16 which feeds the 
positive carbon forward. An examination of Fig. 223-A will, 
I think, show you how it works without further explanation. 
A clamping arrangement, or friction clutch exactly similar to 
the one already described enables the projectionist to feed 
the negative carbon by hand. You will note that the pin wheel 
which rotates star wheel 30 has only one pin, whereas the 
pin wheel which rotates star wheel 16 has two. This is to 
secure the proper ratio of feeding as between the positive 
and negative carbon. 31—31 is the insulating material. 

The lamp is a decided departure in high intensity lamps 
in that it has the usual adjustments which enable the pro¬ 
jectionist to raise, lower, or move the arc sideways, or to 
advance the whole lamp nearer to or farther away from the 
condenser. 

IMPORTANT! —On negative feed screw 29 spring 32 is 
mounted. This performs an important function, in that the 
projectionist is enabled, by grasping negative feed wheel 33. 
to pull the negatiye carbon up into contact with the positive 

. S3K 


590 


HANDBOOK OF PROJECTION FOR 


for the purpose of striking the arc. This action is accom¬ 
plished by a quick, hard pull. Immediately upon releasing 
negative feed wheel 33, the negative carbon drops back into 
its proper position. 

CAUTION.!— It is important that when negative feed wheel 
33 is pulled outward in order to strike the arc, it be released 
the instant contact between the two carbons is accom¬ 
plished. In other words the carbon tips must NOT be held 
in contact with each other. 

CARE OF LAMP.— The projectionist should remember that 
lamps of this type have several revolving parts and that these 
parts work in the comparatively high temperature of the 
lamphouse, to which is added a considerable amount of heat 
conducted directly through the metals of the lamp itself. It 
is therefore important that: (A) The lamp be kept scrupu¬ 
lously clean. (B) Feed screws 13 and 29, negative carrying 
rods 25, the carbon clamp screws and all moving parts of the 
lamp should have “Gradac” rubbed on them occasionally. 
Gradac may be obtained from any good automobile supply 
dealer. 

It is absolutely essential that the contacts between the 
carbon and the metal, both in the positive head, in guide 22 
and in clamp 20 be kept clean. This may best be accom¬ 
plished by securing a rod of carborundum, household size, 
such as is used for sharpening kitchen knives. These rods 
are about 7/16 of an inch in diameter. They may be obtained 
from any hardware dealer at a cost of about ten cents. To 
clean the clamps run the carborundum through three or four 
times, with a twisting motion. This will clean and polish the 
metal, and insure good electrical contact. After cleaning the 
contacts it is important that all carbon dust and scale be 
blown out of the contact. 

EXTRA PARTS. —An extra positive head 6, Fig. 223-B, an 
extra contact brush 7, Fig. 223-B, and an extra spring 24, Fig. 
223-A, should be kept on hand. 

IMPORTANT!!— Positive head 6 and carbon brush 7, Fig. 
223-B, must conform to the size carbons used, in other words, 
if you change the size of your carbons, you must also change 
these two parts, as well as washer 2 , Fig. 223-A. These parts 
may be had in two sizes to fit 7/16th inch carbons, which is 
used for 75 amperes and 13.5 millimeter which is used for 
anything above 80 amperes. 


MANAGERS AND PROJECTIONISTS 


591 


CAUTION. —Washer 2, Fig. 223-A, does not carry current. 

It is neither necessary nor desirable that the set screw in 
washer 2 be tightened down solid. All it does is clamp the 
carbons with sufficient force to carry it forward against the 
friction of the positive head. If you tighten the set screw 
too tight you will very likely break the carbon, or crumble 
it at the point of contact with the screw. 

CAUTION.— The crater of the positive carbon should at no 
time come closer than one inch from the positive head. If 
you allow the crater to burn back too far you will blister the 
metal, and probably ruin the positive head. Be sure and 
maintain a distance of one inch, or even a trifle more. 

ARC GAP.— The proper separation between the negative 
and positive is about one-half inch. You may be able to get 
a fairly good light with a %-mch gap or with a J^-inch gap, 
but you will get a much better light by maintaining the 
proper arc length of about one-half inch. A less arc length 
than this gives too low, and a greater arc length gives too 
high an arc voltage. 

CAUTION.—It is important for health reasons as well as for 
the purposes of ventilating the lamphouse, that the lamp- 
house be connected either to the vent flue or to the open 
air by means of a suitable pipe. Make no mistake, THIS IS 
IMPORTANT! Do not operate a high intensity lamp without 
your lamphouse connected either with a vent flue or with the 
open air. 

NOTICE. —In event that something puts the mechanical arc 
feed out of commission, the lamp may be operated by means 
of a special handle attached to shaft 12. This handle is below 
the base of the lamp, outside the lamphouse and does not 
show in the illustration. Revolving it causes the lamp to 
function just the same as though it were fed by the mechani¬ 
cal arc feed. 

CAUTION. —When operating a lamp of this type it is well 
tb'diave hand bellows for the purpose of blowing out carbon 
dust after cleaning contacts; also for the purpose of blowing 
dust and dirt out of the lamphouse. See Page 869. 

IMPORTANT NOTE.—Full description of other High 
Intensity Arc Lamps will be found under the heading “The 
High Intensity Arc,” beginning on page 773. 


592 


HANDBOOK OF PROJECTION FOR 


The Mechanism 

General Instructions Which Apply to All 
Projectors 

M OTION picture projectors are very frequently sold to 
small town exhibitors who, in the very nature of 
things, are unable to employ competent projectionists, 
and who themselves have very little knowledge of mechanics. 
When a part wears or breaks they are at a loss as to the 
method of procedure necessary to remove same and replace 
it with a new part; also they are unable to make the neces¬ 
sary adjustments of the various parts of the projector 
properly. 

In supplying amusement to what in the aggregate amounts 
to many millions of people who would otherwise be deprived 
of the pleasure of moving pictures, these men are doing a 
distinctly meritorious work. They are entitled to every bit 
of instruction it is possible to give them, including detailed 
instruction with regard to the projector mechanism, because 
any additional knowlege which enables them to project a 
better picture will add to the pleasure of all these millions 
of people who depend upon small town or village moving 
picture theatres for the only form of theatrical amusement 
they have. 

Not only is this true, but it also is a matter of fact that 
even competent, experienced projectionists are offtimes at 
their wit’s end, and commit very serious blunders by reason 
of the fact that but few projectionists, except those in very 
large cities, are able to obtain experience on all the different 
professional moving picture projectors. It is also quite 
true that even many projectionists in large cities lack expert 
knowledge. 

We therefore have no apology of any kind whatsoever to 
make for supplying detailed instructions on projector 
mechanism. To omit them would not only be unfair to the 
industry as a whole, but also to the audiences who patronize 
moving picture theatres, and, moreover, to the projectionist 
himself. The claim that such instructions have a tendency 
to create projectionists has little weight. Even if it did 


MANAGERS AND PROJECTIONISTS 


593 


the projectionist, important as is his function, is but one 
cog in the mechanism of the moving picture industry, and in 
such matters we must first look to the well-being of the 
industry as a whole. 

There are certain instructions which apply to all projectors 
equally. We give them under the form of general instruc¬ 
tions, in order to avoid consuming space by their repetition 
in the detailed instructions for each projector. 

GENERAL INSTRUCTION NO. 1—LUBRICATION.— 

The modern projector is a rather expensive piece of mechan¬ 
ism. The purpose of oiling is to separate moving parts, and 
thus to reduce friction, abrasion and wear to the least 
possible minimum. Any oil will serve this purpose fairly 
well, provided enough of it be used, but in a projector 
mechanism the use of a minimum of oil is highly essential, 
because any excess will be thrown off by centrifugal force, 
get smeared around, and, besides making a dirty mess, will 
get on the films and do a very great amount of damage to 
screen results. 

Oil that is too thin is objectionable for use on a pro¬ 
jector, no matter what its lubricating properties may be, 
because it flies around and runs around too easily. Oil that 
is too heavy is objectionable because projector bearings are 
very closely fitted, and a heavy oil will not work through 
them fast enough, remembering that as the oil passes 
through a bearing it carries out with it any small parts of 
metal that have worn from the bearings, as well as foreign 
dirt which may have lodged there. 

The selection of oil for use on a projector mechanism is 
therefore of the utmost importance, and as a rule, three 
different lubricants are essential: (a) a lubricating oil for 
the various bearings, (b) a lubricant suitable for use in the 
oil well of the intermittent movement, (c) a lubricant for 
the gears. 

We are all familiar with the names of certain much adver¬ 
tised oils, such as “3-in-one.” These oils are, in our opinion, 
without exception absolutely unfit for moving picture pro¬ 
jector lubrication. Their use will, we are firmly convinced, 
shorten the life of a projector very greatly. 

IMPORTANT RULE.— One rule with regard to projector 
lubrication is of huge importance. It should be rigidly 
adhered to by all projectionists. 

Never, under any circumstances, use more than one drop 
of oil in any moving picture projector bearing. 


594 


HANDBOOK OF PROJECTION FOR 


Any more than one drop is very much worse than use¬ 
less. One drop is ample for all purposes of lubrication in 
any bearing of a projector. Any excess over that amount 
will run out of the bearing and be thrown off, making a 
dirty mess, and, to some extent at least, very likely getting 
on the him. 

In our previous books we have recommended a good grade 
of light dynamo oil for the lubrication of projector bearings. 
We see no reason for changing this recommendation. This 
oil can be procured, in bulk, from any dealer in oils at a 
very reasonable rate, but we would recommend that, where 
it is possible, it be purchased from the local electric power 
company, because they are obliged to use a high grade 
lubricant for their dynamos. 

All, or nearly all, the various projector manufacturers 
themselves sell oil which they recommend for use on their 
projector. We can recommend these oils because, in the 
very nature of things, projector manufacturers would not 
select an oil for use on their projectors which would give 
other than good results. 

The manufacturers are interested in seeing their pro¬ 
jectors give good performance, and, knowing that adequate 
lubrication is absolutely essential to the satisfactory per¬ 
formance of any mechanism, naturally they will not recom¬ 
mend or sell anything but an oil suitable for use thereon. 
We therefore amend our former recommendation of dynamo 
oil to the extent of saying: Use either a good light dynamo 
oil or the oil recommended by the maker of your projector. 

OIL WELL LUBRICANT. —The intermittent of the pro¬ 
jector is subjected to exceedingly heavy service. Sixteen 
times every second the driving element strikes the driven 
element what amounts to a heavy, sliding blow, hence, unless 
it run in a high grade, suitable lubricant you may expect 
both these parts to wear very rapidly. 

While we can recommend a heavy bodied, non-carbon oil, 
such as a very heavy dynamo oil, still in this particular thing 
we would suggest that you implicitly follow the instructions 
of the projector manufacturer with regard to intermittent 
lubrication. All, or nearly all, manufacturers of professional 
projectors have for sale a special lubricant which they recom¬ 
mend for use in the intermittent oil well. This lubricant has 
one very important peculiarity, viz.: it will not run out 
through the sprocket shaft bearing. It is a good lubricant for 
the purpose, and we recomend its use. 


MANAGERS AND PROJECTIONISTS 


595 


Never, under any circumstances, put graphite, or anything 
else except pure oil, or whatever is recommended by the 
projector manufacturer, in the intermittent oil well. Graphite 
is a high grade lubricant under some conditions, but it will 
injure or even ruin an intermittent movement, and may do it 
very quickly, too. 

GEAR LUBRICATION. —A light oil, such as is used for 
the projector mechanism bearings, is not suitable for gear 
lubrication. Automobile cylinder oil, bicycle chain lubricant, 
autorjiobile cup grease, or transmission grease, or a good 
grade of vaseline, is very much better. Beeswax also has 
been used by some, and tallow by others. 

WASH OFF GEARS. —If the projector mechanism be of 
the uninclosed type, however, no matter what kind of lubri¬ 
cant is used it will collect dust and dirt constantly, which, 
uniting with the lubricant, forms a grinding paste. It is 
therefore advisable to thoroughly clean the gears of the 
projector mechanism at least once or twice a week. The 
most practical way is to have a shallow dish or pan con¬ 
structed which will fit around one side of the mechanism 
base, under the gears. With the pan in place, while you 
run the projector very slowly, flood the gears with kerosene 
or gasoline from an ordinary squirt can. It, of course, is 
possible to remove the mechanism from the stand and 
immerse the whole thing in kerosone or gasoline, giving the 
crank several turns while the mechanism is so immersed. 
This thoroughly cleanses both the gears and the bearings, 
but is, we think, more trouble than it is worth. If it be 
done, first be sure the intermittent oil well opening is 
closed tightly. 

WASH OUT OIL WELL.—The oil well should be emptied 
at the end of one hundred and fifty hours’ run and filled 
with fresh lubricant. 

From continued use oil becomes “poor.” In ^other words, 
its lubricating powers are lessened through continued use. 
After emptying the oil well it is a good plan to wash it out 
with kerosene, being sure, however, to remove every bit of 
the kerosene, else it will reduce the lubricating quality of 
the new oil, and make it more apt to run out through the 
bearings. 

GENERAL INSTRUCTION NO. 2.— Where the old style 
friction take-up is used it is of utmost importance that the 
take-up tension be set just barely tight enough to take up 


596 


HANDBOOK OF PROJECTION FOR 


the entire reel. Any tension in excess of this is not only 
bad, but it is very bad, particularly if the old style V /2 inch 
reel hub be used. A moment’s study of this matter will con¬ 
vince you of its importance. Throughout the entire process 
of re-winding, the take-up friction will exert precisely the 
same amount of pull on the spindle which carries the take- 
up reel. When the film first begins to wind on the hub of 
the lower reel, the diameter of the film roll will be less 
than 2 inches, if an old type reel be used, therefore the pull 
on the film will be very heavy. As the diameter of the film 
roll increases, however, the pull on the film decreases, until 
when the reel is full it will be very slight. 

In other words, since the pull of the take-up is constant, 
and must be sufficient to revolve the reel when it is full, 
the actual pull exerted on the film at the beginning of the 
process of re-wind, is very many times greater than it is at 
the end. This means that not only is the film wound en¬ 
tirely too tightly at the beginning, and too loosely at the end, 
but also that during the beginning of the process of re¬ 
winding the pull on the film is so heavy that if there is 
excess tension it is quite possible the sprocket holes may be 
strained, or even broken, since the pull is against the lower 
sprocket of the projector. It is even possible, and does 
often happen, that the film is pulled over the lower sprocket, 
and the loyver loop is thus lost, though ordinarily this only 
takes place when a bad splice comes through. 

Excess tension also is apt to pull weak splices in two. It 
is in every way detrimental, therefore the projectionist 
should use every precaution to have his take-up tension set 
exactly right, and “exactly right” is that tension which will 
no more than insure completion of the process of re¬ 
winding. Of late there have been some very excellent de¬ 
vices invented which equalize the take-up pull throughout 
the process of rewinding. Also the split pulley friction take- 
up has been to a very great extent improved by increasing its 
diameter. 

GENERAL INSTRUCTION NO. 3—DIRTY SPROCKETS. 

—It is of the utmost importance that the sprockets of the 
projector be kept perfectly clean. This is important for all 
sprockets, but particularly for the intermittent, because any 
dirt accumulating on the face of the intermittent sprocket 
will cause unsteadiness of the picture on the screen. The 
best method of cleaning sprockets is as follows: Procure a 
rather stiff bristle toothbrush, and either a wide-mouthed 


MANAGERS AND PROJECTIONISTS 


597 


bottle or a small tin can with a cover. If the bottle be used, 
drill a hole through its cork and shove the handle of the 
toothbrush through, so that when the cork is in the bottle 
the brush will reach almost to the bottom. If a can is used 
cut a hole in the lid large enough to admit the brush. 

Partly fill the bottle, or can, with kerosone, and once a 
day (oftener if necessary) examine the sprockets closely, and 
if there is the least bit of gum or dirt on the face of any of 
them scrub it off with the toothbrush wet with kerosene. 

Examine your sprockets carefully at least once a day, 
making certain they are perfectly clean. Dirt on the in¬ 
termittent sprocket will cause the picture to jump, not 
sometimes, but always, while dirt on the upper or lower 
sprocket may cause the losing of one of the loops. 

It is an astonishing thing that some projectionists do not 
grasp the seemingly self-evident fact that the face of the 
intermittent sprocket, or any other sprocket for that mat¬ 
ter, must be kept perfectly clean. We have known of a 
projector mechanism shipped a distance of two thousand 
miles to the factory the complaint being that “the picture 
jumped terribly.” On examination the face of the intermit¬ 
tent sprocket was found to be covered with gum and dirt. 
This was cleaned off in less than a minute, and the machine 
tried out, with the result that the picture was rock steady. 
It seems unbelievable that a man with no more intelligence 
than this would indicate would undertake to project photo¬ 
plays, and reproduce upon the screen the work of some of 
the best artists in the world. Imagine, if you can, sending a 
projector more than two thousand miles merely to have the 
dirt cleaned off the face of its intermittent sprocket, a thing 
the projectionist himself could have done in a minute with 
the aid of a little kerosene and a toothbrush. 

GENERAL INSTRUCTION NO. 4—SPROCKETS IN 
LINE. —It is important that the sprockets of your projector 
be in perfect line with each other and with the aperture. 
With modern projectors there is little possibility of getting 
the sprockets out of line. It is, however, well to test the 
matter when a new sprocket is installed. I cannot give 
definite instructions as to how to test the lining cf the 
sprockets, since they will vary with different makes of pro¬ 
jector. The meaning will, however, be understood by ex¬ 
amining Fig. 224, in which dotted line is presumed to be 
exactly central sidewise in the aperture and the teeth on 
each side of each sprocket must be equidistant from the 


598 


HANDBOOK OF PROJECTION FOR 


line. This may be roughly tested, so far as the intermittent 
and upper sprockets be concerned, as follows: Thread a 
piece of new film into the projector, engaging it with the 
teeth of the upper and intermittent sprockets, closing the 
idlers. Turn the fly-wheel backwards until the film is 
stretched tightly. If the upper and intermittent sprockets 
and the aperture are in the line with each other, that fact 
will be evidenced by the film-edge being out of line with the 

tracks on the aperture plate, 
or the aperture being out of 
center in the film. If the film 
seems to bear equally on both 
edges of both sprockets, and 
the aperture plate tracks are 
not straight with the film, it 
would indicate the probability 
that the aperture plate itself 
is out of true. In some pro- 
pectors this may be easily 
remedied; in others the aper¬ 
ture plate cannot possibly be 
out of true, and the indication 
would be that both the upper 
and intermittent sprockets are 
too far over to one side. Before 
making this test you should 
be sure the intermittent 
sprocket shaft is in exact align¬ 
ment with the cam shaft, be¬ 
cause if one end of the inter¬ 
mittent shaft be high or low, the intermittent sprocket will not 
be square with the film. This condition is not possible except 
on projectors in which either end of the intermittent sprocket 
shaft may be raised or lowered independently of the other 
end. 

GENERAL INSTRUCTION NO. 5—ADJUSTMENT OF 
INTERMITTENT MOVEMENT.— When the intermittent 

movement is on the “lock” its adjustment should be such 
that there will be very little circumferential movement in 
the intermittent sprocket, but care must be exercised that 
the adjustment be not made too close or else there will be 
undue and unnecessary friction of the parts. These adjust¬ 
ments are usually made when the projector is cold, and it 
must be remembered that under the influence of the heat 










MANAGERS AND PROJECTIONISTS 


599 


of the spot, all the parts expand more or less, and that fact 
must be taken into consideration. If the adjustment is made 
close enough so that you can feel the intermittent sprocket 
move just the least little bit when you try to rock it with 
your finger, it will be correct. 

A very little circumferential play in the intermittent 
sprocket does no harm, in fact it is necessary; excessive 
motion will be harmful in several ways. 

Do not attempt to adjust the intermittent as above if 
the cam, the star or the intermittent shaft bearings are 
appreciably worn. 

SPARE INTERMITTENT MOVEMENT.— We strongly 
advise the purchase of a spare, complete intermittent move¬ 
ment, assembled all ready to place in the projector. With 
some projectors the removal of an old intermittent move¬ 
ment and installation of a new one takes quite a bit of time. 
With others an old movement can be removed and a new one 
inserted, all ready to project the picture, in a few moments. 
In order to have steadiness of the picture on the screen it 
is essential that the intermittent movement of the projector 
be in about as nearly perfect mechanical condition as any 
mechanical thing can be. Our reason for advising the pur¬ 
chase of a spare intermittent (one spare for a two-projector 
installation will serve) is that the repair and adjustment 
of so delicate and essential a part of the mechanism can 
usually be better taken care of at the factory or service 
station of its manufacturer than anywhere else. Having a 
spare intermittent, when the intermittent of one of the 
projectors is in need of attention it can be pulled out, the 
new one put in its place and the old one sent to the factory 
or service station by insured parcel post, at an expense of 
a few cents, where it can be put into first class condition 
and returned. The replacement of an intermittent sprocket, 
star or cam, is a very delicate operation, and one which 
should be done at the factory or service station only. 

This is particularly true in the case of the cam and star, 
or cam and diamond in the case of the Power’s projector, 
because it is very difficult, not to say impossible, for the 
projectionist to fit these parts properly. 

Never attempt to put in a new star and try to make it run 
with an old cam, or vice versa. If either a new cam or star 
is to be put in, we would by all means advise that the part 
it is to work with be renewed also, and that new brushings 
be installed as well. 


600 


HANDBOOK OF PROJECTION FOR 


It is possible for the projectionist, by intelligent and very 
careful work, to replace a worm intermittent sprocket. For 
this purpose there is a press made by V. R. Shaw, Motion 
Picture Projectionist, Marian, Indiana, which not only 
presses out the pins, but presses the shaft out of the 
sprocket. It is not an expensive tool, and we commend it to 
the favorable consideration of projectionists, though whether 
it will be placed in the hands of supply dealers or not we 
cannot, at this time, say. Another excellent plan is to get 

a sprocket anvil, illustrated in Fig. 
225, which may be had from the 
E. E. Fulton Company, 3208 Carroll 
Avenue, Chicago, Illinois. With 
this it is possible to drive sprocket 
pins out without injuring either 
the pins or the sprocket. Such an 
anvil can be made. The drawing is 
full size. Never lay the face of a 
sprocket down on a bench and try 
to drive the pins out. Support the 
hub of the sprocket instead. After 
a sprocket has been on a shaft for 
some time it may stick pretty tight. 
The shaft, however, may be driven 
out without danger of injury to 
either it or the sprocket as follows: 
Open a vise about an inch. Across 
its jaws lay two short pieces of 
hardwood board, which for some 
projectors must not be more than 
V\ of an inch thick. In the edge 
of one cut a notch large enough to 
admit the sprocket shaft. Place 
the sprocket with its lower edge 
resting on the boards, the star end 
hanging down between the jaws of 
the vise. Using a short piece of 
No. 6 copper wire for a punch, 
gently tap on the end of the shaft 
and drive it out, being very certain 
it does not fall when released. 
When the old sprocket is 
Figure 225. removed, clean the shaft thor- 









MANAGERS AND PROJECTIONISTS 


601 


oughly, being certain there are no burs or sharp edges on 
pin holes. Wipe off perfectly clean and lubricate with good 
oil, after which push the new sprocket on with a twisting 
movement. If it sticks when partly on, pull off, clean shaft, 
re-lubricate and repeat the twisting movement as you push 
sprocket on again. These parts must and do fit with great 
accuracy, and the twisting is to grind down any slight over¬ 
size of shaft. 

It may or may not take several removals and re-lubrica¬ 
tions, but if persisted in the sprocket will finally be in place, 
and will fit accurately. 

CAUTION. —Intermittent sprockets are pinned on the 
shaft with, taper pins, the small end of which should be 
marked with a center punch mark. If it is not thus marked, 
and you cannot tell which is the small end with your naked 
eye, you can by using a condenser lens for a magnifying 
glass. 

CAUTION.—Don’t hammer on the small end of a taper 
pin with a steel hammer. Either use a punch, or if the end 
of the pin protrudes appreciably, lay a piece of copper on 
the end of the pin and start it by tapping on the copper. 

CAUTION. —In replacing the sprocket be sure you get the 
big end of the hole in the sprocket hub opposite the big 
end of the hole in the shaft, and don’t drive the pins in too 
tightly. Just set them up snug. If you drive too hard you 
will not only make it either difficult or impossible to remove 
them when the time for their removal comes, but you may 
spring the metal of the sprocket or shaft, and thus force 
the whole thing out of true. Remember that the taper of 
the pin is very slight, hence it is a very powerful wedge. 

GENERAL INSTRUCTION NO. 6—END PLAY OF IN¬ 
TERMITTENT SPROCKET. —There must be no appreciable 
end motion of the intermittent sprocket. If there is it may 
produce side motion of the picture on the screen. In most 
modern projectors it is extremely unlikely that such end 
motion will develop, but if it does it must be eliminated. In 
some instances side play is due to the holes in the sprocket 
hub, in which are the pins holding the sprocket to the shaft, 
being worn. If there is end motion and you can find no 
other probable cause, remove one of the pins and examine 
the hole it came out of under a magnifying glass. A con¬ 
denser lens will probably serve. If the hole is out of round, 
then the holes must be reamed out and the new pins put in. 
The Simplex service stations will provide a suitable reamer. 


602 


HANDBOOK OF PROJECTION FOR 


We presume other manufacturers will do the same. Be 
careful to remove no more than sufficient metal to make 
the holes perfectly round. The new pins will, of course, go 
in further than did the old ones, but that is quite all right. 

GENERAL INSTRUCTION NO. 7—WORN SPROCKET 
TEETH.—Never continue to use an intermittent sprocket if 
its teeth have become appreciably worn, because such a 
sprocket is not only very likely to produce unsteadiness of 
the picture on the screen, but will inevitably do serious in¬ 
jury to the working edges of the sprocket holes, thus mak¬ 
ing it impossible under any circumstances to thereafter pro¬ 
ject a perfectly steady 
picture with the film 
that has been thus 
abused. 

EXAMINE TEETH. 

—Once every week the 
projectionist should, 
using a condenser lens 
for a magnifying glass, 
carefully examine the 
wearing surface of the 
intermittent sprocket 
teeth. If he finds any 
indication of undercut, 
such as is shown on 
edges of tooth A, Fig. 
226, or if he finds any, 
indication of “hooking” 
of the tooth, as per tooth B, Fig. 226, the sprocket should be 
immediately replaced with a new one. It is not advisable to 
attempt to turn an intermittent sprocket around so as to use 
the other side of the teeth. 

Worn intermittent sprocket teeth, besides setting up the 
probability of inducing unsteadiness of the picture, and in¬ 
juring the edge of the sprocket holes of the film, have a de¬ 
cided tendency to cause the teeth to climb the sprocket 
holes, thus losing one of the loops. 

The intermittent sprocket teeth do all the work of pulling 
down the film against the braking action of the tension 
shoes, hence are subject to very heavy wear. True, they 
are or should be glass hard, but the friction between the 
teeth and the film is heavy, and is confined to a very small 
surface only, hence it is possible the teeth may show signs 



Enlarged Sprocket, Showing Hooked 
and Undercut Teeth. 


Figure 226. 



MANAGERS AND PROJECTIONISTS 


603 


of wear in a comparatively short time, particularly if the 
pressure of the tension shoes be excessive. 

GENERAL INSTRUCTION NO. 8—GATE IDLERS.— Top 

idler on the gate, or whatever takes it place, is for the pur¬ 
pose of holding the film central over the aperture, and to 
help in preventing side motion of the film. Some of these 
guides have the possibility of adjustment, while in others 
the position is fixed, and cannot be altered. If there is an 
adjustment, the guides should always be kept set close 
enough to prevent any side motion in the film, but not close 
enough to cause any binding. In some of the older type pro¬ 
jectors it is possible to get this adjustment far enough to 
one side that the sprocket holes will show on the screen. 
We believe this, however, is not possible with any modern 
professional projector. 

GENERAL INSTRUCTION NO. 9 —GATE TENSION 
SPRING ADJUSTMENT.—There is no one thing in connec¬ 
tion with the work of the projectionist which receives less 
intelligent attention than the adjustment of the gate tension, 
or in other words the amount of pressure exerted by the 
tension shoes on the film at the aperture. 

It is of course understood that by means of the upper and 
lower loops the strip of film between them is detached from 
the rest of the film, to the extent that it may stop and start 
while the rest of the film runs continuously. 

The office of tension shoes (in the old types of projector 
there were no shoes. The flexible tension spring bore directly 
on the film) is twofold. First, to stop the film when the 
intermittent sprocket stops. Second, to hold the film per¬ 
fectly flat over the aperture during its period of rest. If 
the tension be too weak there will be “over-shooting,” which 
means that the film will not be stopped the exact instant the 
motion of the intermittent sprocket ceases, but, due to mo¬ 
mentum, will continue slightly after the sprocket stops and 
possibly in varying amounts. 

The effect of too much tension is (A) heavy and unneces¬ 
sary wear on the mechanism of the entire intermittent move¬ 
ment, but particularly on the wearing surface of the inter¬ 
mittent sprocket teeth, (B) heavy and unnecessary wear on 
the delicate edges of the sprocket holes in the film, which is 
bad in any event, and will be increasingly injurious if the 
sprocket teeth are in any degree under-cut or hooked It is 
even possible, particularly when ccmbined with high speed 
of projection, that the strain will be sufficient to split or 


604 


HANDBOOK OF PROJECTION FOR 


crack the film at the corners of the sprocket holes. Once a 
film has been subjected to abuse of this kind it will thereafter 
be forever impossible to produce a rock steady picture when 
using that film. 

Summed up, this means that the tension cannot be too 
slack without producing an injurious effect on the screen, and 
it cannot be too tight without injuring both the projector 
and the film itself. 

HOW TO SET TENSION.—Every projector should have a 
tension adjustment in substantial, accessible form. The screw 
by means of which this adjustment is made, besides being 
accessible, should be located away from the heat of the spot. 
Adjustment of the tension cannot be made when there is an 
audience in the theatre. In former editions of this book 
instructions for making this adjustment were given which 
there is no reason to in any degree change or modify. They 
were as follows: 

Thread into the projector a film, the sprocket holes of 
which are in good condition. Run the projector at a speed 
about 10 revolutions of the crank shaft per minute faster 
than your highest speed of projection will be. Continue this 
speed steadily while you so adjust the tension adjustment 
that the picture just begins to crawl up on the screen, which 
means that overshooting has commenced. 

This is as accurate an adjustment as it is possible to make; 
also it is one which anyone can apply, always providing there 
is a tension adjustment on your projector. If there is no 
tension adjustment, then it will be necessary to bend the ten¬ 
sion springs until the desired pressure is had. It is no easy 
job to do this, but it is nevertheless up to the projectionist to 
do it, and any man who has not sufficient regard for the pro¬ 
jector and films placed in his charge to at least safeguard 
them to the extent of properly adjusting the tension is unfit 
to have charge of a projection room. 

GENERAL INSTRUCTION NO. 10 —EMULSION DE¬ 
POSIT.— First run films are frequently sent out with the 
emulsion so soft that it has a strong tendency to deposit on 
the face of the tension shoes, particularly if the tension be 
excessive. Projectionists are obliged to run these films, and 
they experience a great deal of trouble by reason of the 
deposit. The tendency to deposit may be increased by the too 
liberal use of cement in making splices. The emulsion, or a 
mixture of emulsion and cement forms a very hard, unyielding 


MANAGERS AND PROJECTIONISTS 


605 


mass on the polished surface of the tension shoes, which, 
besides causing the tension shoes to jump and clatter, is likely 
to injure the film itself more or less seriously. 

When using a first run film, the surface of the tension shoes 
and the aperture plate track should be carefully examined 
after each reel, (excess of film cement will sometimes deposit 
on the tracks of the aperture plate) and any deposit found 
thereon must be carefully removed. 

BEST WAY TO REMOVE DEPOSIT.— The deposit may be 
removed by scraping it off with the edge of a silver coin, or 
by the use of some other soft metal, but the best way is to use 
a wet cloth. Water softens the emulsion instantly, therefore 
the deposit may be quickly washed off without any possibility 
of injury to the polished parts. 

CAUTION.—Never use a knife blade, screw driver or other 
hard steel instrument to scrape deposit off the tension shoes 
or aperture plate tracks, because by so doing you will scratch 
the polished surface and thus increase the tendency to deposit. 

Many plans have been tried for the elimination of this 
trouble, but the only really practical thing is the lubrication of 
the film track. See Figs. 77-A, Page 271, and 77-B, Page 273. 

It is possible to make a fairly effective film track lubricator 
as per Fig. 77-C, Page 274. 

It is even possible to reduce the trouble somewhat by rub¬ 
bing the tension shoes with the end of a tallow candle before 
threading the projector, or by holding a tallow candle lightly 
against the teeth of the upper sprocket occasionally for a 
few seconds while the film is running. 

GENERAL INSTRUCTION NO. 11—WORN APERTURE 
PLATE TRACKS.— In instruction number 9, we said that one 
of the offices of the gate tension is to hold the film perfectly 
flat over the aperture. This, of course, cannot be done unless 
the surfaces of the aperture plate tracks be themselves true 
and level; it therefore follows that excessive wear of the 
aperture plate tracks may, and probably will, cause a buckling 
of the film over the aperture, and an out-of-focus effect on 
the screen. By this we do not wish to be understood as mean¬ 
ing that buckling of the film over the aperture is always due 
to this cause, but while it may be induced by other causes, 
such as old, shrunken film, worn aperture plate tracks are 
pretty sure to produce the trouble. Buckling of the film over 
the aperature will cause an out of focus effect or an “in and 
out” of focus effect. 


606 


HANDBOOK OF PROJECTION FOR 


The projectionist should carefully examine his aperture 
plate tracks, with reasonable frequency, and should renew 
them as soon as they show any appreciable unevenness of the 
surface. 

GENERAL INSTRUCTION NO. 12—SPROCKET IDLERS. 

—It is essential to proper performance of sprocket idlers that 
the idler set equidistant from the face of the sprocket at 
both ends of the sprocket, and that the distance of the idler 
from the face of the sprocket be a trifle more than the thick¬ 
ness of a film. If the sprocket idler be not carefully and 
accurately set as per the foregoing, there is likely to be more 
or less trouble, particularly at the lower sprocket. The losing 
of the lower loop, while not of course necessarily chargeable 
to improper setting of the lower sprocket idler, nevertheless 
is very frequently due to that cause, particularly if there is 
excessive take-up tension. If the lower sprocket idler be out 
of line with the sprocket, or too far away from the sprocket, 
or close enough to the sprocket to pinch the film, there will 
probably be trouble through losing of the lower loop. 

Never allow your sprocket idler to “ride the film”—that is to 
say, to bear on it with any pressure. This is particularly bad 
if the pressure be greater on one side of the sprocket than 
on the other. Under that condition, the film is likely to 
climb the sprocket at the first bad splice. 

Examine your sprocket idlers frequently, and make sure 
that they are turning freely. If they do not they will soon 
develop a flat spot, which sooner or later means trouble. 
All professional projectors have an adjustment by means 
of which the projectionist may determine the distance of the 
idlers from the face of the sprocket. A fairly good plan is 
to place two thicknessess of film on the sprocket, and then ad¬ 
just the idlers so they rest on the film; with this adjustment 
and only one thickness of film, the idler should be about the 
right distance from the sprocket. 

GENERAL INSTRUCTION NO. 13 —LINING CAM 
SHAFT. —When using a projector in which the adjustment 
between the star and cam is accomplished by turning an 
intermittent sprocket shaft bearing at either end, great care 
should be taken that the intermittent sprocket and the cam 
shaft are kept in perfect alignment with each other. The po¬ 
sition of the cam shaft is not adjustable, but the sprocket 
shaft is raised or lowered by turning the bearing bushings* 
and it is possible, by turning one bushing more than the other, 


MANAGERS AND PROJECTIONISTS 


607 


to get the sprocket shaft lower on one end than the other, 
under which condition the sprocket will not be square with the 
film, and the teeth on one side of the intermittent sprocket 
will have to do most of the work in pulling the film down. 
This matter should be watched very closely when an adjust¬ 
ment is made. 

GENERAL INSTRUCTION NO. 14 —MAGAZINES IN 
LINE. —With modern projectors the position of the upper 
and lower magazines are fixed, and they cannot be located 
wrongly. With some of the older types, however, it is quite 
possible to get the magazine out of line sidewise with the 
sprockets, and this should be guarded against, because a ma¬ 
gazine out of line is likely to cause a great deal of trouble, 
in several different ways. If the lower magazine is out of 
line, the take-up will pull the film sidewise, which will create 
an added tendency to lose the lower loop. If it be the upper 
magazine that is out of line, the film will not approach the 
upper sprocket squarely, which may cause trouble, and in 
any event it will rub against the metal of the fire trap with 
possible damage to the film itself, and certain damage to the 
trap. 

GENERAL INSTRUCTION NO. 15—PROJECTION ROOM 
REELS.—We very strongly recommend that the projection 
room have a full complement of reels, and that the exchange 
reels be used only in the upper magazine for the first run of 
the film after it is received, and in the lower magazine for the 
the last run of the film before shipment. 

THE CONDITION OF REELS SENT OUT BY EX¬ 
CHANGES IS, ALL TOO OFTEN, NOTHING SHORT OF 
AN OUTRAGE. 

They are more often than not a cheap, flimsy affair, with 
a hub and spring clip in more or less wretched condition, 
with their sides bent and wobbly, and very frequently they 
have sharp edges of metal caused by the punchings of the 
reel sides when they are made, which to a greater or less 
extent injures the film. 

Only projection room reels should be used for projection, 
and they should be kept in first class condition. Use of 
reels in bad condition causes an enormous amount of dam¬ 
age to films, both in rewinding and in projecting. Reel sides 
very often rub on the magazine side, thus setting up braking 
action, which, under some conditions, will pull the film in 
two. See Page 322v 


608 


HANDBOOK OF PROJECTION FOR 


Theatre managers will do well to understand the simple 
fact that all unnecessary damage done to films while in their 
own or any other theatre, becomes, of necessity, part of the 
overhead expense in film distribution. If, through careless¬ 
ness in handling films on bad reels, etc., a heavy decrease in 
the life of the film is caused, then whatever the damage is, 
it must, and inevitably will be added to the film rentals. We 
venture the assertion that if theatre managers used a little 
common sense, and insisted that the films be handled care¬ 
fully, and on reels that are in good condition, and that re¬ 
winding be done at the rate of six or seven minutes to the 
reel, instead of one or two minutes, film rentals would within 
a short time be reduced in a very noticeable amount. 

GENERAL INSTRUCTION NO. IS—UPPER MAGAZINE 
TENSION. —In professional projectors there is usually some 
sort of tension device in the upper magazine, the purpose of 
which is to prevent the reel from revolving too freely. It is 
important that this device be so designed that it will not 
catch on loose screws or reel hubs, and that the tension be of 
sufficient amount to just barely keep the film taut at all times, 
and stop the reel instantly when the projector stops. The 
importance of this latter will be realized when we consider 
that if the reel revolves too freely, and the projector be 
stopped when the upper reel is three-quarters or more emp¬ 
tied, and the reel continues to make one or two revolutions 
after the projector has stopped, thus unwinding considerable 
slack film, when the projector is started it is likely to come 
up to normal speed before it takes up all the slack film, 
whereupon the upper reel will be subjected to a sharp jerk, 
which may pull a splice in two, rip out sprocket holes and 
lose the upper loop, or even pull the film itself in two. 

GENERAL INSTRUCTION NO. 17—FILING THE APER¬ 
TURE. —It is sometimes necessary that the form of the pro¬ 
jector aperture be changed, in order to parallel the sides of 
the screen image when there is a pitch in the projection. 
You will find directions for doing this on Page 257. 

GENERAL INSTRUCTION NO. 18.—The Standard aper¬ 
ture now in use and approved by the Society of Motion Pic¬ 
ture Engineers, is .6795 (87/128) of an inch high by .9062 
(29/32) of an inch wide. 

GENERAL INSTRUCTION NO. 19 —MAGNETIZED 
SCREW DRIVER. —The projectionist will find a strongly 
magnetized screw driver a great convenience, particularly 


MANAGERS AND PROJECTIONISTS 


609 


when handling small machine screws, since they may be re¬ 
moved and inserted without danger of dropping them. 

GENERAL INSTRUCTION NO. 20 —THREADING THE 
PROJECTOR. —All projectors thread precisely alike, so far 
as the operating principle is concerned. 

There are differences in the mechanical application of the 
principle but the principle itself is always the same. The film 
comes down out of the upper magazine through a fire-trap, 



Figure 227. 


















































610 


HANDBOOK OF PROJECTION FOR 


engages with upper sprocket A, Fig. 227, and is clamped there¬ 
by to one or more idler rollers, B. The film may pass over 
the upper sprocket as is shown in Fig. 227, or it may pass 
under the sprocket. Having been attached to upper sprocket 
A it is carried down over the aperture, as shown at C, with 
sufficient slack film to form upper loop D. The film is then 
engaged with intermittent sprocket E, and is locked thereto 
by the idler, which may be a roller or may be a shoe, after 
which the gate F is closed and locked shut. The film is now 
engaged with lower sprocket G, Fig. 227, sufficient slack film 
being left to form lower loop H, Fig. 227. The film is locked 
to lower sprocket G by means of idler I, after which it is 
carried down through the fire trap into the lower magazine 
and attached to the take-up reel. Upper and lower loops D 
and H must have sufficient slack film so that when the in¬ 
termittent acts the film between the upper sprocket and the 
top of the gate, and between the intermittent sprocket and 
the lower sprocket, will not be pulled tight. The reason for 
these loops is that whereas upper sprocket A runs continuous¬ 
ly, pulling the film out of the upper magazine and feeding 
it to the intermittent, and lower sprocket G runs continu¬ 
ously, taking the film away from the intermittent sprocket 
and feeding it into the lower magazine, sprocket E only acts 
intermittently, so that the strip of film between the top of 
the gate and the intermittent sprocket is standing still about 
four-fifths of the time, and moving at high speed the rest 
of the time, its high speed while in movement exactly equal¬ 
ling the total travel of the rest of the film. In other words, 
while upper sprocket A feeds three-quarters of an inch of 
film in a given time, which we will assume to be 5/80 of a sec¬ 
ond, the film between the upper end of the gate and the in- 
mittent sprocket moves exactly three-quarters of an inch in 
1/80 of that time, standing still 4/80 of the time. The offices 
of the upper and lower loops are to enable the constantly 
running film above and below to join with the intermittently 
running film over the aperture. 

GENERAL INSTRUCTION NO. 21—THREAD IN FRAME. 
—Modern practice demands that the film be threaded in 
frame. By this it is meant that when threading the projec¬ 
tor the projectionist must so place the film that one whole 
photograph will register exactly over the aperture, neither 
the upper or lower frame line being visible. This can be ac¬ 
complished in several ways. The projectionist may look 
through the lens while placing the film, or he may hold a 


MANAGERS AND PROJECTIONISTS 611 

lamp in front of the lens and look through the other way. 
At least one projector manufacturer, the Power’s, places a 
small battery lamp inside the mechanism, which may be tem¬ 
porarily lighted while framing. 

No matter what plan be adopted for accomplishing the pur¬ 
pose, however, the picture should never be projected to the 
screen out of frame. Such work is crude in the extreme, and 
brands the projectionist as a very slip-shod, careless work¬ 
man, except possibly in one projector installation where 
threading must be done in the absolute minimum of time. 

GENERAL INSTRUCTION NO. 22—REVOLVING SHUT¬ 
TER.— The revolving shutter is an extremely important and 
integral part of the optics of the projector. Its function is 
to close the lens, or, in other words, to cut off the light from 
the screen during the time the intermittent movement is acting 
and moving the film over the aperture. 

It is absolutely essential to intelligent work that the pro¬ 
jectionist have a complete understanding of all those various 
things relating to and connected with the revolving shutter. 

To begin at the, beginning, there is no such thing as a “mov¬ 
ing picture,” or a “motion picture.” What we term moving 
or motion pictures, is really nothing more or less than the 
display of a series of snapshot photographs, taken at the rate 
of sixteen or more per second, and displayed to us so rapidly 
that one photograph blends into the next, thus forming the 
optical illusion of motion. 

Beginning at a frame line between two pictures, measure 
one foot of film, and you will find thereon precisely sixteen 
complete pictures. Except in the matter of size these 
pictures in no way differ from ordinary snapshot photographs. 
They are presumed to be taken at the rate of sixteen per 
second, but as a matter of fact in modern practice the speed 
of taking very frequently exceeds this considerably. As the 
film passes through the projector these photographs are, by 
means of the intermittent mechanism, successively posed over 
the aperture, and while so posed are projected, one after the 
other, to the screen. The purpose of the intermittent move¬ 
ment of the projector is to pull the film down across the 
aperture precisely three-quarters of an inch, and to leave it 
over the aperture for an infinitesimal period of time. At the 
rate of sixty feet of film per minute, the time each picture 
remains over the aperture is one-sixteenth of a second, less 
the time it requires to move the film down, which ordinarily, 


612 


HANDBOOK OF PROJECTION FOR 


is about one-fifth of one-sixteenth of a second, or 1/80 of a 
second. We may therefore say that at the rate of sixty feet 
per minute, 4/80 of a second is consumed by the actual pro¬ 
jection of the picture, and 1/80 of a second is consumed in the 
removal of one photograph and the substitution of the next 
—in the pulling down of the film. 

WHY THE LENS MUST BE CLOSED.— If, however, the 
change of photographs over the aperture be made with the 
light projected constantly to the screen, there will be streaks 
of white up and down across its surface. The reason of this 
is as follows: White makes a greater impression on the eye 
than do colors of less brilliancy. Suppose we project a mov¬ 
ing picture to the screen without any revolving shutter— 
with the light projected constantly. Suppose in this scene 
there is a man in evening dress, with a broad expanse of white 
shirt front. The dark colors of the evening dress make little 
impression on the eye, but the dazzling white of the shirt front 
makes a very great impression, and as the film moves and the 
figure of the man in one photograph is substituted for the 
figure of the man in the next, as the figure of the man in the 
first photograph is jerked down out of the way the eye will 
see and follow the brilliant whiteness of the shirt, though it 
will not see and follow the darker clothing. Also, as the 
other figure comes into view the eye will quickly catch the 
white of the shirt, and not see the dark clothes until the 
figure comes to rest. We would therefore have a white 
streak across the screen. These white streaks are technically 
known as “travel ghost.” 

Due to this phenomenon, it is necessary that the lens be 
closed during the time the intermittent movement is in action 
and the film moving, and this is the function performed by 
the revolving shutter. 

The revolving shutter of a projector (except in the case of 
the one and one-and-a-half-to-one shutter, the action of 
which will be explained further on) revolves exactly once to 
every complete cycle of the intermittent movement. If a 
certain edge of the master blade of the shutter occupies a 
certain position with relation to the lens when the intermittent 
begins to act, it will occupy precisely the same position the 
next time the intermittent begins to act, having meanwhile 
made one complete revolution. 

Without any film in the projector, open the gate, block the 
automatic fire shutter up and project the white light to the 


MANAGERS AND PROJECTIONISTS 


613 


screen while you run the projector very slowly. You will ob¬ 
serve that during the time the intermittent sprocket is in 
motion the master blade of the revolving shutter cuts off all 
the light from the screen. You will also observe that, accord¬ 
ing to whether you have a two-wing or a three-wing shutter, 
all the light is cut off from the screen two or three times dur¬ 
ing each complete cycle of the intermittent, or during each 
revolution of the shutter. 

In projection, what we therefore have on the screen is a 
succession of flashes of more or less brilliant light, and a 
succession of almost equal periods of time when no light from 
the lens reaches the screen. 

After running very slowly, as above directed, gradually in¬ 
crease the speed of the projector and you will find that when 
you get up to normal projection speed there will be an 
apparently uninterrupted screen illumination. 

WHY MORE THAN ONE BLADE.— What we call “flicker” 
is the visibility of the period during which the screen is dark. 
The revolving shutters of all motion picture projectors have 
more than one blade. The reason for this is that, since light 
interruptions must be at the rate of 36 or more per second in 
order to render them invisible, the one-blade shutter would 
not be practical, because the light interruptions would come 
too far apart. As already explained-, in motion picture pro¬ 
jection the screen is alternately more or less brilliantly lighted 
and totally dark, insofar as light from the lens is concerned. 

FLICKER.— The human eye is a peculiar instrument. It 
will transmit to the brain, as separate impressions, a certain 
number of impressions per second. Beyond that number, 
the impressions become merged into each other, so that the 
effect is that of continuity. This involves what is termed “per¬ 
sistence of vision,” which is the peculiarity of the eye which 
makes the illusion of “moving pictures” possible. If the flashes 
of light and darkness come too far apart, or if they be dis¬ 
proportionate to one another, then the eye will perceive them. 
Under this condition persistence of vision operates incom¬ 
pletely, and instead of the illusion of even, steady illumina¬ 
tion, the recurring flashes of light and darkness will be per¬ 
ceived in the form of what is termed “flicker.” Flicker is a 
very serious matter indeed, in that it causes eye strain exactly 
in proportion to its amount. If excessive the strain on the 
eyes is very great and very highly injurious. Experience has 
taught that with a low illumination value, such as is repre- 


614 


HANDBOOK OF PROJECTION FOR 


sented by an ordinary cloth screen and an arc lamp using 25 
amperes, the rate of interruptions of the light may be as low 
as 36 per second without flicker being objectionably visible. 
With a more brilliant illumination, however, such as is had 
with a brilliant screen surface and 60 or more amperes of 
current, we find it is necessary to increase the interruptions 
to between 55 and 60 per second in order to render them in¬ 
visible, or in other words to obtain the effect of even, con¬ 
tinuous screen illumination. 

MASTER BLADE. —The blade which cuts the light from 
the screen while the intermittent sprocket is moving is va¬ 
riously called the “master” blade, “working” blade, “main” 
blade and the “interruptor” blade. We have selected 
master blade as the most appropriate term. In addition, the 
shutter has one or more additional blades, commonly termed 
“flicker” blades, the purpose of which has already been 
described. 

The function of the master blade is to close the lens while 
the intermittent movement is in action. When the intermit¬ 
tent sprocket starts to move the master blade of the shutter 
comes in front of the lens and entirely shuts off the light from 
the screen, passing from in front of the lens and permitting 
the passage of the light to the screen the instant the intermit¬ 
tent sprocket comes to rest. From this we see that, in theory, 
the shutter must be so set or “timed” that its master blade 
will cover the lens, and shut off the light from the screen at 
the exact instant the intermittent begins to move, and un¬ 
cover the lens at the exact instant the intermittent sprocket 
comes to rest. This, however, is to some extent modified. As 
a matter of fact the lens need be only about three-quarters 
closed when the intermittent sprocket begins to move, and 
may still be slightly open when the intermittent movement 
ceases. This is because of the fact that, with the lens three- 
quarters closed, the light on the screen is very dim, and the 
impression on the eye therefore diminished to a point where 
the movement of the picture over the aperture cannot be per¬ 
ceived. If, however, the timing of the shutter be such that 
the lens is open too much, either when the film starts to move 
or is coming to rest, travel ghost will result. 

SHUTTER BLADE WIDTH.— What may be termed the 
optical balance of the revolving shutter has directly to do with 
the width of the shutter blades with relation to each other, 
and with relation to the light openings. It is a well estab- 


MANAGERS AND PROJECTIONISTS 


615 


lished fact that a three-winged shutter having three blades 
of equal width with each other, and of equal width with the 
light openings, produces the best effect in that a flickerless 
picture can be had at a lower speed of projection than with 
any other available shutter. 

A shutter of this kind cannot be used except under certain 
circumstances which will be explained under “intermittent 
speed and the shutter.” It has been very thoroughly demon- 
onstrated that a three-wing shutter with the flicker blades of 
different width than the master blade, and with the light 
openings of different widths, produces an excellent effect, but 
this unbalancing may only be done in a certain prescribed 
way, one feature of which is that on either side of the master 
blade there shall be a comparatively wide opening, and be¬ 
tween the two flicker blades an opening of relatively narrow 
width. 

INTERMITTENT SPEED AND ITS EFFECT ON THE 
SHUTTER. —To the uninitiated it may seem a very simple 
matter to have a 50-50 shutter, i.e., a shutter in which all blades 
are of equal width with each other and with the openings, 
but as a matter of fact, it is not. As has already been pointed 
out, the master blade of the shutter must be wide enough to 
cover about three-quarters of the lens opening, or to cut 
about three-quarters of the light beam when the intermittent 
sprocket starts to move, and still have about three-quarters 
of the beam covered when it comes to rest. Remembering 
that the shutter revolves once to every cycle of movement 
of the intermittent, it will be seen that the longer the time 
consumed by the intermittent in movement, the wider must 
be the master blade of the shutter. 

In other words, the shorter the period of time the intermit¬ 
tent is in movement with relation to the time it is at rest, the 
less width of master shutter blade is necessary. Conversely, 
the slower the movement the wider the master blade must be. 

The correct way of describing the speed of the intermittent 
movement is in degrees. The driving member (cam) of the 
intermittent movement is circular, and revolves continuously. 
Every circle is divided into 360 degrees. If the driven mem¬ 
ber (star) is engaged with the driving member (cam) and in 
movement during 60 degrees of the revolution of the cam, 
then the movement is a “60 degree movement.” correspond¬ 
ing to a five-to-one movement, because the total cycle of 
movement is divided into six periods, one of which (60 de- 


616 


HANDBOOK OF PROJECTION FOR 


grees) represents the time during which the star and inter¬ 
mittent sprocket will be in motion. A true 60 degree move¬ 
ment should allow us to have a 50-50 three-wing shutter be¬ 
cause there are three wings and three light openings, or in 
other words, 6 divisions, and since the time of movement it¬ 
self is equal to one of the six periods, the shutter blades and 
the shutter openings may all be equal with each other, always 
provided there be no lost motion in the mechanism. 

NOTE: This is not strictly correct except in theory be¬ 
cause of the fact that the lens has considerable diameter the 
greater part of which must be covered at opening and closing. 

In considering the speed of the intermittent we have only 
to determine whether it is a “six-to-one,” a “five-to-one” 
or whatever it may be, and then divide 360 by the number of 
cycles in the movement (a five-to-one is, for this purpose, a 
six-cycle movement, a four-to-one a five-cycle movement and 
so forth) in order to reduce the matter to degrees. For in¬ 
stance, with a four-to-one we have 4+1=5, and 360-^-5=72, 
therefore the four-to-one is a 72-degree movement. With such 
a movement the intermittent would be in action 72 degrees of 
the entire cycle, and the master blade of the revolving shut¬ 
ter would have to be 72 degrees wide if the light beam had no 
diameter and if there was no lost motion in the gearing be¬ 
tween the intermittent and the shutter. As a matter of fact, 
however, a sufficient width would have to be added to the 
master blade to cover about three-quarters of the diameter of 
the light beam, and to allow for lost motion, so that a four-to- 
one movement would mean a very bad optically balanced re¬ 
volving shutter, which would set up tendency to flicker at 
low speeds, and cut off a very great percentage of the light. 
The width of such a blade is easily calculated, as follows: 
Measure distance center of shutter shaft to center of diameter 
of projection lens. Multiply this measurement by two. Mul¬ 
tiply that result by 3.1416 and divide that result by five, or 
the total number of cycles in the movement, meaning that if 
it be a six-to-one movement, then the divisor would be seven. 
The result will be the necessary width of master blade in 
inches at center of light beam, measured on the arc of a 
circle, if the light beam had no diameter. 

It must be remembered that whereas we may not hope to 
have a revolving shutter cut much less than fifty per cent, 
of the light, still we may have it cut decidedly more than 
fifty per cent., and the nearer we can approach to the best 


MANAGERS AND PROJECTIONISTS 


617 


possible condition the greater the percentage of the light we 
will be enabled to get through to the screen, and the better 
will be the condition as regards flicker. 

LIGHT BEAM DIAMETER. —From the foregoing it will 
be observed that the diameter of the beam of light at the 
point at which it is cut by the revolving shutter is a matter 
of much importance, since the wider the light beam the 
greater length of time will be required for the shutter blade 
to cut through it, therefore the wider must be the master 
blade of the shutter. 

To grasp the meaning of this, remember that the master 
blade of the shutter travels at a uniform rate of speed, con¬ 
suming, let us assume, 5/80 of a second in making one com¬ 
plete revolution. It will therefore require a longer space of 
time for the edge of the blade to cut through a beam two 
and one-half inches in diameter than it will to cut through 
a beam one inch in diameter. Also it is evident that since 
the speed of the blade, as measured in inches per second, 
increases directly as the distance from the center of the 
shutter shaft is increased; the greater the distance from 
the center of the shutter shaft to the center of the light 
beam, the less time will be consumed by the edge of the 
master blade in cutting across a beam of given diameter. 
Therefore the greater the distance from the center of the 
shutter shaft to the center of the light beam the less im¬ 
portant increased diameter of the light beam becomes. 

Figure 228 shows the effect of added distance center of shut¬ 
ter shaft to center of light beam. At 2 45/64 of an inch a 
1.5 inch circle occupies 32 degrees and 12 minutes. At 3 17/64 
inches the same diameter circle covers only 26 degrees and 
28 minutes, while if the distance be 3^4 inches the same circle 
occupies only 22 degree and 54 minutes. A 1.5 inch circle 
represents what is popularly known as a “quarter size lens.” 
From this we see that added distance from center of shutter 
shaft to center of light beam makes for better conditions as 
to width of master blade of revolving shutter. 

No matter what the distance may be, however, the .less 
the diameter of the light beam the quicker the blade will 
cut across it, therefore since the master blade must cover 
three-quarters of the beam when the film begins to move, 
and continue to ‘cover three-quarters of it until the film has 
stopped, it is apparent that the less the diameter of the beam 
the narrower may be the master blade, therefore it follows 
that: 


618 


HANDBOOK OF PROJECTION FOR 


The shutter blade should be set at the narrowest point of 
the light beam in front of the projection lens. 

We therefore see that insofar as concerns necessary 
width of the master blade there are three governing ele¬ 
ments, viz.: speed of intermittent movement, distance from 
center of shutter shaft to center of light beam and diameter 
of light beam. 



AERIAL IMAGE. —The front surface of the converging 
condenser lens is focused at a point in front of the projec¬ 
tion lens, except in the case of very short focal length pro¬ 
jection lenses, in which case the image may be inside the 
lens barrel. The distance the aerial image will be from the 
























MANAGERS AND PROJECTIONISTS 


619 


projection lens will depend upon the distance of the con¬ 
denser from the projection lens and the focal length of the 
projection lens itself. As a general proposition the revolv¬ 
ing shutter should be set at the point of the aerial image. 
This does not, however, always hold good. 

TO FIND THE IMAGE. —The location of the proper shut¬ 
ter position may be found in three different ways, as fol¬ 
lows: (a) place a metal plate, in the center of which is a 

hole about one-quarter of an inch in diameter, over the face 
of the converging lens and project the white light to the 
screen. Blow smoke in front of the projection lens, and you 
will see that the resultant beam gradually narrows down and 
then spreads out again. The correct shutter position is at 
the narrowest point, .(b) Project the white light to the 
screen and slowly pass some opaque object down through 
the light beam at varying distances in front of the lens. 
You will find a point at which either two shadows appear 
simultaneously on the screen, one at the bottom and one at 
the top, or else the whole screen “dissolves” into darkness. 
In the first case the point at which the shadows meet exact¬ 
ly in the center of the screen is the correct shutter position. 
In the second case the point at which the dissolving effect 
is most perfect is the right place, (c) Project the white 
light to the screen and hold a piece of black paper or some 
very dark colored, non-gloss object in the light beam in 
front of the projection lens, moving it slowly away from 
the lens until a sharp image of the converging lens of the 
condenser appears thereon. This test may be made more 
accurate by first printing some word on the face of the con¬ 
verging lens, using ordinary ink, and then focusing the 
printing. 

The last method locates the aerial image and you can see 
at a glance whether it is advisable to set the shutter at that 
point or not, because you can measure the diameter of the 
beam at that point. If the beam at that point is either more 
narrow, or even as narrow as it is at any other point, then 
that is the place for the, shutter, but if at a point nearer the 
lens the beam is more narrow (as is the case under some 
conditions) then the shutter should be set at the most nar¬ 
row point of the beam. 

DISSOLVING EFFECT. —The reason we say the revolv¬ 
ing shutter should be set at the aerial image unless the beam 
be actually of greater diameter at the image than it is nearer 
the lens, is because of the fact that at the aerial image there 


620 


HANDBOOK OF PROJECTION FOR 


is a dissolving effect, which may or may not enable the use 
of a less width of master blade. In any event, we believe it 
will produce a better effect. 

THE WHY AND WHEREFORE.—Remember this. There 
is no manner of use in setting your shutter at the most nar¬ 
row point of the light beam unless you take advantage of 
the opportunity that act affords, which is to reduce the 
width of the master blade. MERELY TO CHANGE THE 
LOCATION OF YOUR SHUTTER FROM A WIDER TO 
A MORE NARROW POINT IN THE BEAM HAS NO 
EFFECT WHATEVER except that if you have travel ghost 
it may be made less or eliminated entirely by moving the 
shutter to where the beam is more narrow—has less 
diameter. 

The gain is just this: If your shutter is cutting the beam, 
without travel ghost at a point at which it, the beam, is 
wider than it is at some other point, then if you change the 
location so that the master blade cuts the beam at a more 
narrow point you can trim sofnething off the master blade, 
thus enabling you to work more efficiently—to cut a less 
percentage of the light, and to obtain a better optically 
balanced shutter. 

HOW TO TRIM SHUTTER BLADE.— There is a right 

way and a wrong way to do everything. After you have 
located your shutter at the narrowest point of the beam, the 
next thing is to determine how much can be trimmed off the 
master blade, and while you can probably estimate the 
amount pretty closely by slowly revolving the shutter and 
seeing where its edge is with relation to the light beam when 
the intermittent starts and when it stops, still if you get too 
much trimmed off your shutter blade is ruined. It is there¬ 
fore advisable to proceed as follows: Get from a print shop 
a piece of stiff card-board about twelve inches square, such 
as heavy business cards are printed on. Remove the revolv¬ 
ing shutter from its hub. Lay the metal blade on the paper 
and trace its blade edges thereon, afterwards cutting the 
paper so that you have a paper shutter with blades and 
openings exactly the same width as those of the metal blade. 
Never mind the outside rim. You may not think it. but if 
you are careful not to bend the paper so that you wrinkle it, 
such a paper blade will run for weeks, or even months. 

Now place your paper blade in the hub, put it on its spin¬ 
dle and set the shutter correctly, though the necessity for 
setting may be avoided by making a mark on the hub of the 


MANAGERS AND PROJECTIONISTS 


621 


shutter and on the metal blade before removal, and then 
making a mark on the same place on the paper blade, setting 
the two together when you assemble the paper blade and 
the hub. 

Having installed your paper shutter, gradually trim off 
just a little bit at a time from one edge of the master blade 
until a tiny bit of travel ghost appears. Next trim off a little 
at a time from the other edge of the blade until a little bit 
of travel ghost appears. Having done this, remove the 
paper blade, lay it on the metal blade and cut the metal 
blade so that it is just a little wider on each side than the 
master blade of the paper shutter. This added width will 
kill the travel ghost, unless you have trimmed down too 
much on your paper master blade. You can now re-install 
the metal blade with the assurance that it is cutting the least 
possible percentage of the light. 

Having done this, it is well to consider carefully whether 
a corresponding amount can be taken off the flicker blade. 
If the flicker blades are already more narrow than the mas¬ 
ter blade, then we would not advise this, and this is the con¬ 
dition you will probably find with the three-wing shutter. 
With the two-wing shutter the blades will probably be the 
same width, in which event you can trim off the flicker 
blade edges as much as you did off the master blade. 

SHUTTER AND LOCAL CONDITIONS.—It is a very 
serious mistake to assume that the revolving shutter sent by 
the projector manufacturer is necessarily correct. It usually 
is not correct, though that is no fault of the manufacturer, 
who cannot possibly know under what local conditions any 
given projector will be obliged to work. 

The manufacturer usually sells his projector through sup¬ 
ply houses. Any given projector may have to work under a 
local condition requiring either a very short focal length or 
a very long focal length projection lens, and a projection 
lens of maximum or minimum diameter. The manufacturer, 
therefore, is compelled to send a revolving shutter which 
will prevent travel ghost under any except the very worst 
conditions. The dealer (supply house) usually knows little, 
and perhaps cares less about the optics of projection, there¬ 
fore he is unable to determine what particular shutter blade 
width will be required under any given local condition. 

It is up to the projectionist himself to fit the revolving 
shutter to the local condition, and any projectionist who is 
unable to do this, and to do it intelligently, is not a compe- 


622 


HANDBOOK OF PROJECTION FOR 


tent projectionist. He cannot get the best results except 
where, purely by chance, the shutter sent happens to fit the 
condition under which it must work. 

We might add that: 

Tendency to flicker increases with screen brilliancy and 
with the size of the picture. Conversely, it decreases with 
decrease in screen brilliancy and decrease in size of picture. 

THE SHUTTER AND ALTERNATING CURRENT.— 

Where 60 cycle A. C. is used at the arc the use of the three- 
wing shutter is inadvisable for the following reasons: 60 
cycle A. C. reverses its direction (alternates) 120 times per 
second, or 7,200 per minute. When a projector running at 
the rate of 60 feet of film per minute is equipped with a 
three-wing shutter, the light is cut 2880 times a minute. Half 
of the alternations per minute is 3,600, and if the cycle of the 
current happens to be not quite 60 (as often is the case) but 
55 to 58 instead, it would require but just a little over-speed¬ 
ing of the projector to bring the wings of the shutter into 
synchronism with one side of the alternations. Under this 
condition, if the wings happen to cut the light at the point of 
its greatest brilliancy (See Fig. 4, Page 16), the brilliancy 
of the light on the screen would be diminished by probably 
one-half, or maybe even more. And this is what very often 
does take place where an attempt is made to use a three- 
wing shutter in conjunction with a 60 cycle A. C. projection 
arc. The net result is that screen brilliancy will die down 
and come up time after time, and in a way which is very 
mysterious to the uninitiated. This is because of the fact 
that in order to dim the light the shutter must be precisely 
in synchronism with the alternations, and while this may 
occur, it is not at all likely the synchronism would be long 
maintained because an almost infinitesimal variation of the 
speed of the projector would throw the shutter out of syn¬ 
chronism with the alternations, with result that the screen 
brilliancy would come back to normal. Put in simple words 
the efifect of this is that screen brilliancy will alternately 
diminish and increase; decreasing when the shutter blades 
happen to be in synchronism with the one side of the alter¬ 
nations, and increasing when they are not. 

TWO-WING SHUTTER FOR 60 CYCLE.— For the fore¬ 
going reason it is advisable that a two-wing shutter be used 
with 60 cycle A. C., unless the speed of projection be such 
as will preclude the possibility of the shutter, blades and 
alternations getting into synchronism. 


MANAGERS AND PROJECTIONISTS 


623 


TWO-WING AND THREE-WING SHUTTERS.— Except 
in the case of 60 cycle A. C. we advise the use of the three- 
wing shutter, provided the condition is such that it can be 
at least fairly well optically balanced. It is true that as a 
general proposition the two-wing shutter will cut a some¬ 
what less percentage of the light than the three-wing shut¬ 
ter, but it is also true that with modern brilliant projection 
it is seldom possible to run a picture at normal speed when 
using a two-wing shutter, without producing flicker. 

It does not necessarily follow that under all conditions the 
three-winger will produce appreciably less flicker at the 
given speed than the two-winger. We would suggest to tne 
projectionist that he test the matter by installing a three- 
wing shutter and getting it into the best condition the local 
condition will allow. Project white light to the screen and 
find out how low a speed it can be run at before flicker ap¬ 
pears. Then put on a two-wing shutter and make the same 
test. If the two-wing shutter produces no flicker at the 
lowest speed you use, then the two-winger is to be pre¬ 
ferred, but if it does produce flicker at your lowest speed, 
then the three-winger is to be preferred, because you can get 
all the really necessary screen brilliancy with it, and current 
is cheaper than flicker. Also it is better to have photoplays 
run at the proper speed, even though it be at the expense of 
some screen brilliancy. 

We have explained all this at considerable length in order 
to give projectionists a clear understanding of the various 
points involved. 

SETTING THE SHUTTER.— The setting of the revolving 
shutter is to the novice a very mysterious operation. It is, 
however, almost childishly simple once the underlying 
principle is understood. The master blade of the revolving 
shutter is, or should be, stamped with some distinguishing 
mark. If it is not, then you are safe in selecting the widest 
blade as the master blade. Loosen the shutter so that it 
may be revolved by pulling a little while you hold the pro¬ 
jector fly-wheel stationary. Turn the fly-wheel until the 
intermittent sprocket is just barely ready to move, pull the 
shutter around in the direction it normally runs until its 
edge covers about three-quarters of the lens, tighten tne 
holding screws, but not so much that you cannot pull the 
shutter around on its hub or shaft by exerting a moderate 
amount of force. Thread a film into the projector, prefer¬ 
ably one having a white lettered title with black back 


624 


HANDBOOK OF PROJECTION FOR 


ground. Project it, and if there are white streaks up and 
down from the letters, or from white objects in the picture, 
move the shutter slightly by pulling it around. If this makes 
the matter worse, then you have moved it the wrong way. 
Move the shutter until the white streaks disappear, where¬ 
upon you are all right. That is all there is to “setting the 
shutter.” 

If there should be travel ghost both up and down it is 
evidence that the master blade of the shutter is not wide 
enough. A condition of this kind may be eliminated by riv¬ 
eting a small, light piece of sheet metal to each edge of the 
shutter blade (each edge to preserve the balance) or by 



Figure 229. 


moving the shutter to a more narrow point of the light ray, 
if it is not already at the narrowest point. 

ONE-AND-A-HALF-TO-ONE SHUTTER.— This type of 
shutter is in effect a three-wing shutter, though it has but 
two blades. This is by reason of the fact that instead of 
revolving once to each complete cycle of the intermittent, 
as do other shutters, it makes one-and-a-half revolutions to 
each cycle of the intermittent. This means that if we num¬ 
ber its two blades 1 and 2, and No. 1 is master blade at the 
movement of the intermittent, No. 2 acts as flicker blade and 
No. 1 does also, No. 2 coming in front of the lens as master 
blade at the next movement of the intermittent. This type of 
shutter has the advantage of high speed, which causes the 



MANAGERS AND PROJECTIONISTS 625 

edges of the master blade to cut across the light beam faster, 
hence increased diameter of beam is not of so much impor¬ 
tance as with the regular type shutter. Beyond this we do 
not feel it to be the province of this work to discuss the rela¬ 
tive merits of the two types. The Baird projector uses the 
one-and-a-half-to-one shutter. 

GENERAL INSTRUCTION NO. 23 — TAKE-UP. —Most 
modern projectors are equipped with a take-up device which 
more or less automatically equalizes the pull on the film, 
and that a very efficient equalizer is essential is made evi¬ 
dent in Fig. 229 in which A represents the lower sprocket of 
the projector. Suppose with the film attached to the one 
and one-half inch diameter hub of an ordinary reel as per 
Fig. 229, and that a lever, G, be attached to the shaft carry- 



Figure 230. 


ing the reel, if we place a one-pound weight at the end of 
the lever, it is very evident that the amount of pull on the 
film at X will be very many times more than the pull on the 
film at Y, and there lies the kernel of the take-up nut. The 
lower, or take-up reel is driven by the projector mechanism 
which runs at a continuous and presumably steady rate of 
speed, feeding sixty or more feet of film to the take-up 
reel per minute. You will readily see that under condition 
X, the reel will have to run very fast as compared to its 
necessary speed under condition Y in order to wind up the 
film. We see from this that the take-up reel which is driven 
by a power having steady speed, must itself run at a speed 
varying from very fast to very slow, which means there 
must be slippage somewhere between the driving and the 
driven members. 

One way of accomplishing this is shown in Fig. 230, in 






626 


HANDBOOK OF PROJECTION FOR 


which 8 is a pulley driven by a belt connecting with the pro¬ 
jector mechanism, 1 is a shaft upon which this pulley rides. 
Pulley 8 is not attached to the shaft, but revolves freely 
thereon. Six is a cast iron disc attached to shaft 1 by means 
of a pin or set screw, so that the two must revolve as one 
member. Thirteen is the key which locks the take-up reel 
to shaft 1, and part 2 is the lock which holds the reel on 
the shaft. Between pulley 8 and disc 6 is a washer, 7, made 
of fiber. The action is as follows : Spring 12 is placed on 
the end of shaft 1 and against pulley 8. It is followed by 
collar 14 in which is a set screw. It will readily be seen that 
pulley 8, disc 6, and washer 7 will be clamped together by the 
pressure of spring 12, and that the amount of pull pulley 8 
will exert on disc 6 through washer 7 before it will slip on 
washer 7 will depend upon the amount of pressure spring 12 
exerts, which same may be altered by altering the position 
of collar 14. 

This is the old style friction take-up; its trouble is that it 
must be set tight enough to revolve the reel under condition 
Y, which means that it will exert a very heavy pull on the 
film under condition X, Fig. 229. All the old style take-up 
did was to allow sufficient slippage between drive-wheel 8 
and disc 6 to accommodate the slowing up of the reel as the 
film roll grew larger. This condition has the objections that 
it (a) tends to cause the losing of the lower loop, (b) it 
exerts an unnecessary and highly injurious strain on the per¬ 
forations of the film, (c) it has a tendency to pull weak 
patches in two and (d) it has a very decided tendency to 
scratch the first hundred feet of film. 

CAUTION. —Projectionists who are using old style take- 
ups should be very careful to set the tension as lightly as is 
possible without danger of failure to rewind the entire film. 


THE MORE YOU KNOW THE 
GREATER VALUE YOU ARE 
TO YOUR EMPLOYER. 



MANAGERS AND PROJECTIONISTS 


627 


The Power’s Projector 

T HE Power’s projector may be had in several models, the 
latest being the six-B, with Type E lamphouse. 

Figs. 231 and 232 supply dimensional data which will 
be of value in planning the projection room. 

Type E lamphouse is illustrated in Fig. 233. It is 11.5 
inches wide, 18 inches front to back and 22 inches from floor 
to roof. The doors- are well braced and double walled, with 
a half-inch air space between the two walls through which 
air circulates. The metal used is heavy Russian iron. 

The top is so arranged that it may be connected with a 
pipe leading to the open air or to the projection room vent 
pipe. In the right hand door is a pin-hole projector with a 
ground glass screen, held out two inches by a metal casing, 
upon which screen an image of the crater is projected. Up¬ 
on this screen lines either are, or may be scratched to repre¬ 
sent the proper 55 degree angle position of the crater. The 
other door has an ordinary observation hole covered by a 
colored glass. 

In the right hand back corner is a small incandescent lamp 
so arranged that it lights when lamphouse door is opened. 

The condenser mount is illustrated in Fig. 234. The lenses 
are carried in a metal holder which is calculated to equalize 
the expansion of the thin edge and thick center of the lens, 
and thus reduce breakage. The lamp rack-bars are three- 
quarters of an inch square. The bearing through which they 
slide is 2^4 inches long. The surfaces which grip the car¬ 
bons are 1^4 inches long, of cast iron, dull nickeled. The 
carbon clamp screws are 5/16 inch in diameter; the leverage 
for clamping the carbons is ample. 

USE GRAPHITE. —The carbon clamp screws and other 
working parts of the lamp must be kept lubricated with 
powdered graphite. A dry, unlubricated carbon clamp 
screw is an abomination and a nuisance. The construction 
of the lamp, as a whole, is rigid and good. On the front of 
the bearing carrying the rack bars is a heat shield of asbes¬ 
tos. The lamp has all the necessary, usual adjustments. 
The dowser is inside. It has two handles so that it may be 
operated from either side of the projector. These handles 


628 


HANDBOOK OF PROJECTION FOR 



Figure 231. 

AA—Speed control knobs. B—Maximum possible angle projector may 
be set at, which is 23% degrees. C—Screw for adjusting projector angle. 
D—Lock to hold projector at desired angle. E—Ground glass screen 
upon which image of crater is projected. FF—Telescoping legs, by 
means of which the projector, as a whole, may be lowered 11% inches. 
G—Vent cap ; may be lifted off for connection to a vent pipe. H—Pro¬ 
jector motor switch ; handle on both sides. II—Magazines take 1,000- or 

2,000-foot reels. 

NOTE.—At extreme possible angle (28% degrees) total height of pro¬ 
jector is increased to 6' 9.5", floor to top of vent cap, and total front to 
back length is increased to 4' 10". Outlet for arc lamp circuit should 
be four feet from front wall, plus whatever distance bottom of front legs 
will be from the wall. 










































MANAGERS AND PROJECTIONISTS 


629 


are at A, Fig. 234, which figure shows the condenser holder 
tipped down to get at the lenses. When tipped back up it is 
locked into place by handle B. C, Fig. 234, is the screw by 
means- of which the distance between the collector and con¬ 
verging lenses is altered. 


INSTRUCTIONS FOR CARE AND ADJUSTMENT OF 
POWERS PROJECTOR MECHANISMS.— While at first 
glance these instructions may 
seem complicated, they are in 
fact very simple and quite easily 
applied. In what follows it is 
intended to provide all necessary 
instruction for anything the 
projectionist may be called upon 
to do in connection with Power’s 
projector mechanisms and speed 
controls and we have tried to 
make the instructions so plain 
that even the uninitiated may 
follow them without much 
trouble. 

The Power’s mechanism are 
of the “open” type, which means 
that there is no inclosing casing. 

The projector may, by a very 
simple arrangement, be set at 
varying heights from the floor. 

It may be tilted to any angle 
within the limits of practical 
projection, either up or down. 

In referring to these instruc¬ 
tions the numbers indicate the 
illustration in which they occur 
and the particular part in the 
illustration, thus : 659, P. 2, indi- igure 

cates the part numbered 659 in plate 2, which in this case is 
the intermittent sprocket idler roller bracket. 



INSTRUCTION NO. 1—REMOVING MAIN DRIVING 
GEAR AND SHAFT. —To remove main driving gear 630, P-4, 
and its shaft 631, P-4 and P-7: First remove crank 632, P-5, 
and the taper pin 789, P-2, which engages the slot in the 
hub of the crank. The taper pin 789, P-2, should be driven 
out from its small end. Having removed the pin, the shaft 
and gear may be withdrawn, and if desired the gear may be 

























630 HANDBOOK OF PROJECTION FOR 

removed from the shaft by driving out the taper pin in its 
hub. 

On mechanism equipped with the adjustable shutter 
bracket, it will be necessary, before proceeding with instruc¬ 
tion No. 1, to remove the adjusting spindle P. 9. This is ac¬ 
complished by removing the nut D which is secured by a set 
screw, then turning the knurled knob A to the left, when 
facing the gate, until the spindle B is free from the split nut 
C. The spindle B can then be withdrawn from the shutter 
bracket and gear 630 removed as directed above. 

INSTRUCTION NO. 2—TO REMOVE SHAFT 618, P-4, 
CARRYING GEARS 620 AND 619, P-4.— First follow in- 



Figure 233. 

















MANAGERS AND PROJECTIONISTS 


631 


structions No. 1, then loosen screw 782, P-2, whereupon the 
shaft and gear may be withdrawn from the gear side. 

INSTRUCTION NO. 3—REMOVING AUTOMATIC FIRE 
SHUTTER GOVERNOR COVER.— To remove the auto¬ 
matic fire shutter governor cover 623, P-2, loosen screw 740, 



Figure 234. 


A—Dowser Handles. B—Lock Handle. C—Screw to change spacing 

of lenses. 

P-2, backing it off considerably, as it is countersunk into the 
shaft. This releases cover 623 (shown on the left in Plate 9). 
If the cover does not pull off readily, tap gently on the end 
of the shaft, at the same time pulling on the cover. 

CAUTION. —Do not try to pry the cover off by inserting 
a screw-driver point between part 623 and 624, P-2. If you 
do you will probably succeed in ruining your governor. 

INSTRUCTION NO. 4—TO REMOVE FRICTION CAS¬ 
ING OF AUTOMATIC FIRE SHUTTER 624, P-2.— Follow 








632 


HANDBOOK OF PROJECTION FOR 


instructions No. 3, after which remove 798, P-7, whereupon 
part 624 may be pulled away. 

INSTRUCTION NO. 5—TO REMOVE AUTOMATIC 
SHUTTER LINK 628 AND LEVER 627, P-7.— Follow in¬ 
structions No. 3 and No. 4, after which the parts may be re¬ 
leased by taking out a screw on the reverse side of part 624. 

INSTRUCTION NO. 6-ADJUSTING FIRE SHUTTER 
GOVERNOR. —Should automatic fire shutter 697, P-1, fail to 



Figure 234-A. 


The Power’s Late Model Lamp. 


drop, examine lever 627 and links 628, P-7, and see that they 
work freely and are not bent. Usually the binding of these 
parts is responsible for the sticking of the fire shutter. If 
this is not found to be the seat of the trouble, remove cover 
623, P-2 (see instruction No. 3), and carefully examine 
springs 717, P-9, also examine the inside edge of friction cas¬ 
ing 624 and see if track “Y,” Plate 9, is smooth, as it should 
be, and not scratched or rough. If it is rough or scratched, 
carefully polish track “Y” by using No. 00 emery cloth. 





MANAGERS AND PROJECTIONISTS 


633 


CAUTION. —Do not use coarse emery cloth or you will 
only succeed in making matters worse. 

Should the automatic fire shutter fail to rise properly, first 
try injecting a drop of heavy oil in the oil hole on top of 
624, P-2. The clutch shoes 625, P-9, act by centrifugal force, 
which throws out weights 626, P-9, against the action of 
springs 717, P-9, thus forcing friction shoes 625 against tra^ck 
on part 624, P-9. The friction thus engendered revolves 
casing 624 in clock-wise direction, which forces lever 627, 
P-7, ahead and raises shutter flap 697, P-1. Do not use thin 
oil on the automatic shutter, as it tends to reduce the fric¬ 
tion too much. Use heavy oil sparingly. Should the fire 
shutter rise too quickly, or should the governor develop un¬ 
due friction, thus making the mechanism pull hard, it will 



Figure 234-B. 

Power’s Late Model Arc Lamp with Terminal. 


probably be found that springs 717, P-9, have become weak¬ 
ened. This may be remedied by installing new springs or 
by stretching the old ones. Another possible cause of fail¬ 
ure of the fire shutter to act, or to act too slowly, is the 
binding of the screws at the top or lower end of link 628, 
P-7. This link must swing perfectly free. In the centre and 
lop of fire shutter flap 697, P-1, is a pin. This pin not only 
serves to hold the flap to its spindle and prevents its slipping 
circumferentially, but it also prevents the shutter from ris¬ 
ing too high. Therefore, it should not be allowed to be¬ 
come loose and fall out. 

INSTRUCTION NO. 7—REMOVING TOP ROLLER 
BRACKET. —Top roller bracket 612, P-2 and 7, may be re¬ 
moved by taking out stud 710, P-7. 



634 


HANDBOOK OF PROJECTION FOR 


INSTRUCTION NO. 8.—REMOVING TOP SPROCKET 
IDLER ROLLER 609, P-2. —This may be removed by loosen¬ 
ing screw 733, P-2, pulling the shaft out and taking out the 
collar next the roller. This roller should be replaced if there 
is any indication of flat spot on its surface. Before adjusting 
these rollers, see general instruction No. 12. 

INSTRUCTION NO. 9—REMOVING TOP AND LOWER 
SPROCKETS. —To remove the upper sprocket 617, P-7, first 
remove the upper apron 629, P-2, by removing the two 
screws, one at each corner. Then loosen the screw in the 
centre of the hub of sprocket 617, P-2, pulling the sprocket 
off the shaft. The lower sprocket 646, P-2, can be removed 
by loosening the small screw in the centre of hub of sprock¬ 
et and pulling sprocket off the shaft. See general instruction 
No. 3 concerning keeping sprockets clean. 

If film seems to bear equally on both edges of both 
sprockets and the aperture plate tracks are not straight 



619 

620 


630 


747 

603 

674 


705 


783 


697 
693 
696 
689 
67 7 
678 
671 


686 

669 

46 

782 

769 


1732 *- 
74 
743 - 


748 -- 

749 — 
65 
644 - 


653 - 

658 - 

650 

795 - 


Plate 1, Figure 235. 














































MANAGERS AND PROJECTIONISTS 


635 


with film it would indicate aperture plate out of true. Gen¬ 
tly drive its top one way or the other, as is required, to 
square it with the film. The first thing to do, however, be¬ 
fore making this test is to be certain your intermittent 
sprocket shaft is in exact alignment with camshaft. 

INSTRUCTION NO. 10—TENSION OF UPPER IDLER 
ROLLER. —Upper sprocket idler roller 609, P-2, is held to 
the sprocket by a flat spring, 615. Should this spring at 
any time become too weak, it may be strengthened by re¬ 
moving the idler roller bracket (see instruction No. 7) and 
bending the top of the spring outward until the desired 
tension is obtained. 

INSTRUCTION NO. 11—REMOVING THE GATE.— 

The entire gate, including cooling plate 696, P-1, automatic 
fire shutter flap 697, P-1, and hinge 690, P-1, may be removed 



Plate 2, Figure 236. 























































636 


HANDBOOK OF PROJECTION FOR 


by taking out screws (three of them) 747, P-1. In replacing 
the gate, before tightening up screws 747, P-1, be sure that 
the top gate guide rollers 691, P-3, centre properly with the 
aperture plate. After replacing the gate project the white 
light to the screen. If there is a shadow at the top, bottom 
or side, open the gate. If the opening of the gate removes 
the shadow, then it means that your gate is not properly 
centred, and you must loosen hinge screws 747 and move 
gate until the shadow disappears. Be careful, however, that 
the gate guide rollers 691, P-3, are kept spaced central with 
aperture and sprocket, as per Fig. 224. 

INSTRUCTION NO. 12—REMOVING AND ADJUSTING 
TENSION SHOE. —Tension shoe 694, P-2, may be removed 
by first pulling out the pin in the gate-hinge 690, P-1, after 
which remove screws 738 (one on either side), P-2. This 
releases the tension shoe. 

INSTRUCTION NO. 13—REMOVING TENSION 
SPRINGS. —Between the face of the gate and cooling plate 



Plate 3, Figure 237. 



































MANAGERS AND PROJECTIONISTS 


637 


^9o, P-1, are the tension springs and the tension spring 
equalizer. Should it at any time be necessary to remove 
either of these, take out flat-head screws just above and be¬ 
low the cross-bar joining tension shoe tracks 694, P-2. This 
will release cooling plate 696, P-1, and expose the parts. In 
replacing, be sure that the little flat spring which acts on 
gate latch 693, P-1, rests against the latch and not on top 
of it. 

INSTRUCTION NO. 14—REMOVING COOLING PLATE. 

—(See instruction No. 13.) 



647 723 


792- 

728- 

761 

A- 

775- 

649- 


785 


631- 

63a 

787- 


635 

633 

634 


749 
66 , 
77I&772 
768 I 


620 

618 

621 


Plate 4, Figure 238. 

INSTRUCTION NO. 15—ADJUSTING TENSION.— The 

pressure of the tension shoes is governed by screw 732A, 
P-1. Setting this screw inward increases- the tension and 
conversely loosening the screw decreases it. THE TENSION 
SPRINGS SHOULD BE KEPT SET EXACTLY RIGHT. 
SEE GENERAL INSTRUCTION NO. 9. 

INSTRUCTION NO. 16—APERTURE PLATE.— Aperture 
plate 687, P-2, may be taken off by removing screws 735 
(four of them) and pulling the plate away. In replacing the 
aperture plate, proceed as follows: Put the plate in place 



































638 


HANDBOOK OF PROJECTION FOR 


and insert the four screws holding it, tightening them down 
just enough so that by tapping lightly on the edge of the 
plate it may be moved either way. Now project the white 
light to the screen and move the aperture until the upper 
and lower lines of the light are level on the screen where¬ 
upon tighten up the four screws. 

CAUTION. —In removing parts of this kind, remember 
that the screws are small. Do not lay them down anywhere, 
depending upon luck to find them. Have a cigar box or 
small receptacle of some kind in which to place all screws, 
or in lieu of that, replace them in the holes when you take 
the part away. Then you will know where they are when 
you want them. A magnetized screw-driver is a fine thing 
to handle small screws with. See general instruction No. 19. 



Plate 5, Figure 239. 










































MANAGERS AND PROJECTIONISTS 


639 


INSTRUCTION NO. 17—ADJUSTING GATE LATCH 
SCREW. —The right-hand edge of the face of the gate and its 
left-hand edge should set an equal distance away from the 
face of the machine casting, since otherwise the tension shoe 
will exert greater pressure on one side than will the other. This 
is regulated by the gate latch screw 797, P-2. This screw 
should be set at a sufficient distance to bring the entire gate 
square with the face of the machine casting and the lock nut 
thereon should then be set up tight to prevent any change in 
this adjustment. 

INSTRUCTION NO. 18—REMOVING INTERMITTENT 
ROLLER BRACKET.— Roller bracket 659, P-2, may be re¬ 
moved by taking out the screw in its hinge, first, however, 
having loosened screws 795, P-2, holding the spring 663, P-2. 
The distance of the idler roller which this bracket carries 
from the intermittent sprocket may be varied by tightening 
or loosening screw 746, P-2. See general instruction No. 12. 



Plate 6, Figure 240. 
































640 


HANDBOOK OF PROJECTION FOR 


To vary distance of idlers from sprocket first loosen nut on 
its outer end, then turn the bracket clear up and the head of 
the screw will be found underneath. The further this screw 
is backed out, the further the roller will be from the sprock¬ 
et, and vice versa. After the proper adjustment is made, be 
sure to tighten lock nut on screw 746, P-2. The tension of 
this bracket is governed by flat spring 663, P-2. This may be 
made greater or less by bending the spring. If it is to be 
made less, just bend the upper end of the spring down, but 
be careful and do not bend it too much. 

INSTRUCTION NO. 19—REMOVING AND ADJUSTING 
APRON. —Apron 669, P-1, may be taken off by removing two 
screws (one on either side) near the roller near its base. 
The adjustment of this apron is quite important. Should the 



Plate 7, Figure 24L 














































MANAGERS AND PROJECTIONISTS 


641 


film make a chattering noise in going through the machine, 
carefully bend the ears at the lower end of apron 669, P-1, 
which carry the rollers, ahead slightly, being careful to bend 
each one the same amount. If this remedies the trouble, well 
and good. If it helps, but does not remedy it, then try bend¬ 
ing it a little more. If it makes it worse, bend the rollers 
back slightly r . You can do no damage by bending these 
apron ears, provided you keep the rollers square with the 
sprocket, that is to say, equidistant from the sprocket. To 
test this, measure from the face of the hub of the roller to 
opposite teeth on the lower sprocket. 

INSTRUCTION NO. 20—REMOVING AND ADJUSTING 
LOWER SPROCKET IDLER BRACKET.— Lower sprocket 
idler bracket 653, P-1, may be removed merely by taking out 
its hinge screw, first, however, loosening screws 795, P-1, 
holding flat spring 658. The distance of the roller which 



Plate 8, Figure 242. 


















































642 


HANDBOOK OF PROJECTION FOR 


this bracket carries from the sprocket (see General Instruc¬ 
tion No. 12) is determined by the position of the screw 749, 
P-1. Spring 658, P-1, should supply sufficient tension to this 
bracket to hold it firmly in place when it is closed down, but 
this may be overdone. The tension- of this bracket should 
not be sufficient to cause the sprocket teeth to punch 
through, or even indent the film should it climb the sprocket. 
This adjustment calls for the exercise of judgment. If it is 
too tight, damage may and probably will be done to the film. 

INSTRUCTION NO. 21—TO REMOVE FLYWHEEL 672, 
P-3. —Remove screw 709, P-3. If you cannot start this screw 
with an ordinary screw-driver, grind down the broad end of 
a file to make a screw-driver for this purpose. Having re¬ 
moved this screw, place the point of the screw-driver right 
up close against the hub on the opposite side of the wheel, 
and tap gently until the wheel becomes loose. In replacing 
the flywheel be sure that groove C in pinion 677, P-7, con¬ 
nects properly with the key on the camshaft. In order to 
accomplish this, insert the point of a screw-driver between 
the lugs carrying brackets 659, P-2, and the collar on shaft 
675, P-2, and pry gently downward. This will hold the spin¬ 
dle stationary while you twist the wheel until the slot and 
key come opposite each other. CAUTION: Between pinion 
677, P-7, and the hub of the casting it fits up against is a thin 
steel washer, 742, P-7. This washer fits on the larger diam¬ 
eter of the shaft and you must be careful that it is precisely 
in place before the wheel is forced on, or you will have trou¬ 
ble. When the wheel is in place, tighten up screw 709, P-3, 
tight. 

INSTRUCTION NO. 22—REMOVING TOGGLE GEAR.— 

To remove toggle gear 678, P-1 and 1, follow instructions No. 
21, then loosen the screw in the upper end of connecting link 
682, P-7, whereupon the gear and spindle may be pulled out. 
The adjustment of this gear is a very important matter. 
The gear must be exactly centered between flywheel and pin¬ 
ion 677, P-1 and 7, and gear 680, P-3. The toggle gear is car¬ 
ried by connecting link 682, P-7, and its position with rela¬ 
tion to the gears on either side of it is determined by the 
position of the casting 684, P-7. Should a grind develop in 
this gear, first having made sure that connecting link 682, 
P-7, is held snugly in its ways by casting 685, P-7, using a 
soft metal punch, tap lightly first one way and then the 
other against casting 684, P-7, the idea being to slip the cast¬ 
ing slightly against the pressure of the screws which hold it.. 


MANAGERS AND PROJECTIONISTS 


643 


The casting cannot be moved much, but sometimes enough 
movement may be accomplished to remove or reduce a 
grind. 

INSTRUCTION NO. 23—ADJUSTING CONNECTING 
LINK. —Connecting link 682, P-7, plays an important part, 
and must be kept tight in its ways. If by shaking horizontal 
bar 683, P-7, you are able to move connecting link 682, in its 
ways, then it is too loose and may be tightened as follows : 
First loosen screws 727, P-7, then release lock nuts on 744, 
P-7, tighten screws 744 a trifle, next retighten screws 727, 
P-7, and try the framing lever. If it is still too loose, then 
you can give them a little bit more, but be careful and do 
not get them too tight or your framing carriage will bind. 
In making this- adjustment do not set screws 744 in so much 
that the connecting link fits snugly while screws 727 are 
loose, because if you do, when you tighten screws 727 the 
whole thing will be clamped solid. Be sure that screws 727 
and the lock nuts on screws 744 are set tight. 

INSTRUCTION NO. 24—REMOVING LOWER SPROCK¬ 
ET SHAFT. —To remove lower sprocket shaft, loosen screw 
782, P-1, and pull the shaft out to the left. 

INSTRUCTION NO. 25—REMOVING LARGE IDLER 
GEAR. —To remove large idler gear 640, P-4 and 8, remove 
the mechanism from the stand, then remove motor attach¬ 
ment, if projector is motor operated, by removing screws 
730 and 759, P-8, when motor attachment will come away 
from the mechanism. Turn it bottom side up and, looking, 
you will see the shaft which holds this gear, and on it, rest¬ 
ing against the mechanism casting, a brass collar, the stock 
number of which is 642, P-5. Move the flywheel until the 
set screw in this collar comes into view. Loosen the set 
screw and you may then pull the gear and its shaft out. 

INSTRUCTION NO. 26—REMOVING THE LOOP SET¬ 
TER. —Loop setter fork 768, P-4, may be removed by first 
following Instructions No. 24 and 25. Then remove stud 775, 
P-4, which will release the fork and clutch 766, P-4. Loop 
setter cam 761, P-4, is removed by following Instructions 23, 
24 and 25, loosening the two large screws in its face and 
pulling it off the shaft. Should it be necessary to remove 
the loop setter arm, carrying roller, 769, P-3, or the spring 
which provides tension therefor, first follow Instructions 24 
and 25, then loosen screws 792 (three of them), P-4, when 
the loop setter arm may be pulled out though the hole in 
the mechanism casting. The replacement of these parts is 


644 


HANDBOOK OF PROJECTION FOR 


merely a reversal of the process of their removal, but in re¬ 
placing them be sure that all screws, particularly screws 
792 and the screws in cam 761, be set up tight. In replacing 
the loop setter, be careful that roller 769, P-3, lines with the 
lower sprocket, or, in other words, that the roller sets per¬ 
fectly "‘square with the film,” since otherwise when the loop 
setter acts, the pull would be all on one side of the film and 
this might, and probably would, cause trouble. 

INSTRUCTION NO. 27—ADJUSTING LOOP SETTER 
SCREW, 728, P-4 is for the purpose of adjusting or regulat¬ 
ing the throw of the loop setter arm and roller 769, P-3. 
This screw should be so adjusted that roller 769, P-3, rests 
about half-way between the lower sprocket and the top of 
the front cross bar in the base of the mechanism. 



Figure 243. 

INSTRUCTION NO. 28—THE SHUTTER BRACKET.— 

When a new machine is received, shutter bracket 637, P-4, will 
be folded down against the mechanism, and shutter blade 700, 
P-6, will be tied to the mechanism. Raise shutter bracket 637, 
P-4, up until it is in a horizontal position, as shown in plate 4, 
and screw 787, P-4, has engaged the hook on the upper part 
of the bracket, first having backed screw 787 out sufficiently 
so that the hook will pass in behind its head. Now, having 
raised the bracket clear up, tighten screw 787, P-4 and 5, 
tight, and then tighten screw 788, P-5, up tight. CAUTION: 
Do not tighten screw 788 until you have tightened screw 787, 
because if you do it will probably cause the shutter spindle 
to bind in the bracket. 

INSTRUCTION NO. 28^4—TO REMOVE THE SHUTTER 
BRACKET. —The entire shutter bracket 637, P-4, may be re¬ 
moved from the machine by first following Instructions No. 
1, 24 and 25, and loosening screws 787 and 788, P-5. Then drive 


MANAGERS AND PROJECTIONISTS 


645 


out the taper pin in the hub of gear 680, P-3, and drive out 
shaft 681, P-3, carrying with it on the opposite end gears 633 
and 634, P-4. To drive out shaft 681, use a brass punch 
slightly smaller in diameter than the shaft. 

NOTICE. —On mechanisms equipped with the adjustable 
shutter bracket, it will be necessary, before proceeding, to 
remove the shutter bracket, to first remove spindle B, Fig. 
249. To do this proceed as follows: Remove nut D, Fig. 249, 
which is secured by a set screw, which must first be loos¬ 
ened. Next turn knurled knob A, Fig. 249, to the left (coun¬ 
ter clockwise) as you face the screen, or as you face the 
mechanism gate if the projector is off the stand, until it is 
disengaged from split nut C. Spindle B may then be with¬ 
drawn from the bracket and the bracket may be removed as 
above directed. 

INSTRUCTION NO. 29—REMOVING SHAFT 681, P-3, 
AND GEARS 633 AND 634, P-3. —See Instruction No. 28. 

INSTRUCTION NO. 30— INSTALLING SHUTTER DRIV¬ 
ING GEARS, 633, 634 AND 635, P-4.— DO NOT ATTEMPT 
IT. If these gears need replacing, it will be necessary to 
send the mechanism to the factory or to a thoroughly com¬ 
petent repair man. The same applies to shutter shaft 636, 
P-4. It would hardly be possible for the projectionist to re¬ 
place gears 633, 634 or 635, or to put in a new revolving shut¬ 
ter shaft, and get the parts adjusted so they would run 
smoothly. 

INSTRUCTION NO. 31—REMOVING SHUTTER FROM 
HUB.— In P-6, we see a three-blade shutter. This blade 
may be changed to a two-blade, using the same hub, by 
loosening screw 739, P-6, pulling the shutter off its shaft and 
removing the three screws 791, P-6, in the back of its hub. 
This releases the shutter blade, which may then be changed 
to another one of different design if desired. 

INSTRUCTION NO. 32—SETTING THE SHUTTER.— On 
projectors not equipped with adjustable shutter bracket as 
per Fig. 249, shutter 700, P-6, may be set by loosening screw 
790, P-6, in hub, which will allow the outer hub to revolve 
on the inner, and enable the projectionist to set the shutter 
in any desired position. When a new mechanism is received 
the revolving shutter shaft will be folded down. Raise it 
up, loosening screw 787, P-5, until it will enter slot in shut¬ 
ter bracket. Raise shaft as far as it will go and set up screw 
787, tight. Next tighten screw 788, P-5, which also holds 


646 


HANDBOOK OF PROJECTION FOR 


bracket. Be sure you tighten both these screws after raising 
shaft into place. Next place shutter on shaft with hub out 
as shown in P-3, with screw 739, P-6, in V groove in shaft. 

Should travel ghost (streaks up and down from letters of 
titles, or flashes of white up and down from white object in 
pictures) develop at any time, it may be eliminated by reset¬ 
ting the shutter. Loosen one of the screws 790 and slack off 
on the other one until shutter ran be slipped by applying 
some pressure. If streaks are up hold flywheel stationary 
and revolve the top of the shutter away from you slightly, 
and, with a-title having white letters on an opaque back¬ 
ground, try it. If 'the streaks are down, pull top of shutter 
towards you. Keep slipping shutter slightly and trying until 
streaks disappear. Then tighten up screws 790. When 
travel ghost develops, first be sure screw 739, P-6, is set up 
tight. To set a new shutter, proceed as follows: Place 
shutter on shaft as shown in P-6, with hub towards end of 
shaft. Set screw 739, P-6, in groove and tighten it. Loosen 
screws 790, P-6, so that shutter revolves freely on inner hub. 
Open gate and turn flywheel forward until intermittent 
sprocket is just at point of moving. Set shutter as shown 
in P-6 and tighten one of 790 slightly. Then proceed as 
directed for travel ghost. For very short focal length lenses 
the Nicholas Power Company will supply a special shutter 
on application. Their two-blade shutter should always be 
used on 60-cycle A. C. The blade with stamp B, P-6, on it 
is the master blade, and the only one to be considered at all 
in setting the shutter. 

Travel ghost may be caused by (a) screw 739, P-6, being 
loose, (b) Collars 638, P-4, not set up snugly against bear¬ 
ing, thus allowing end play in shutter shaft, (c) Gear 680, 
P-3, loose on its shaft, (d) Gear 633, P-4, loose on its shaft, 
(e) Badly worn gears. Any one of these things, or all com¬ 
bined, may cause travel ghost.. Screws clamping shutter 
blade in flanges of hub being loose might also be responsible 
for it. 

TRAVEL GHOST may also be caused by master blade 
being too narrow, in which case it may be removed by mov¬ 
ing the shutter to a position where it will cut the light beam 
at a point where it has less diameter, if there is such a point, 
or by making the blade itself wider. 

NOTICE.— On mechanism equipped with an adjustable 
shutter bracket, knob A, Fig. 249, should be turned until split 
nut C is located central between bearings E and F. Having 


MANAGERS AND PROJECTIONISTS 


647 


done this you may make a roughly correct adjustment of the 
shutter as before directed, completing the fine adjustment 
by turning knob A, Fig. 249, in the required direction after 
the projector is running. 

INSTRUCTION NO. 33—REMOVING OIL CASING 
COVER. —To remove oil casing cover 674, P-4, follow In¬ 
structions No. 24 and 25. Next remove screws 793 (three of 
them), P-4, and tap lightly on the hub of the cover to break 
the shellac joint. 

In placing this cover back, scrape the edges lightly, but be 
sure and get them perfectly clean. Then smear edge of the 
cover (not casing edge, but the cover edge only) with thick 
shellac and clamp the cover in place. It is better if the 
shellac dries a little before you put on the cover, but don’t 
let it dry too much. CAUTION: DO NOT PUT ON TOO 
MUCH SHELLAC. If you do it will squeeze out into the 
interior of the oil casing and get between the pins and the 
cam, and may do serious injury to the intermittent move¬ 
ment. Instances have been known where an excess of shellac 
has broken the geneva pins. 

INSTRUCTION NO. 34— REMOVING CAMSHAFT AND 
CAM. —First follow Instructions Nos. 21, 24, 25 and 33. Then 
loosen the two screws 743, P-2, in bushings 670 and 671, P-2. 
Then loosen the two set screws in the collar on shaft 675, 
P-2, just above arrow head, 670, P-2, move the collar over to 
the right, and, with a small fine file smooth ofT the burrs 
caused by the set screws. The shaft and cam may now be 
pulled up to the left. CAUTION: In replacing the shaft, 
do not forget to put collar on and tighten the two screws 
743, P-2. 

INSTRUCTION NO. 35—REMOVING INTERMITTENT 
SPROCKET, ITS SHAFT AND PIN CROSS AS A UNIT.— 

To remove the intermittent sprocket, its shaft and the pin 
cross as a unit, first follow Instructions Nos. 19, 21, 24, 25, 
33 and 34. Next loosen screws- 743, P-2, and the entire unit, 
including the large bushing in which the shaft runs, may be 
pulled out through the oil well. 

INSTRUCTION NO. 36—ALIGNING SPROCKETS.—It 

is of the utmost importance that upper sprocket 617, P-2, 
intermittent sprocket 667, P-2, and lower sprocket 646, P-2, 
and aperture plate be all kept exactly in line. The align¬ 
ment of intermittent sprocket, upper sprocket and aperture 
plate may be tested by placing a short strip of film (don’t 


648 


HANDBOOK OF PROJECTION FOR 


use worn film for this purpose) in the mechanism with the 
gate open. Place it on the intermittent sprocket and close 
idler bracket. Engage sprocket holes on film with teeth of 
upper sprocket and turn flywheel backward until film is 
stretched tightly, being careful that teeth are in centre, side- 
wise of sprocket holes. If sprockets and aperture are not in 
perfect alignment the fact is readily detected by the film 
edge not being in line with tracks on aperture plate, or 
aperture not being central in film. 

If film seems to bear equally on both edges of both 
sprockets and the aperture tracks are not straight with film, 
it would indicate aperture plate out of true. Gently drive 
its top one way or the other, as is required, to square it with 
the film. The first thing to do, however, before making the 
test is to be certain your intermittent sprocket shaft 666, 
P-2, is in exact alignment with camshaft 675, P-2. 

INSTRUCTION NO. 37—REMOVING THE FRAMING 
CARRIAGE. —To remove the entire framing carriage of the 
mechanism, first remove the aperture plate (see Instruction 
No. 16) and the gate (see Instruction No. 11). Next remove 
the screw 741, P-4, turn the machine around and, looking in 
through the lens hole, you will see perpendicular rods 669, 
P-2, the top ends of which are held in cast lugs. Loosen the 
set screws in these lugs and in similar lugs at their lower 
ends, and pull these perpendicular rods out from below. 
Next remove horizontal bar 63, P-3, by taking out screw 731, 
P-3. The carriage may then be taken from the machine. 

INSTRUCTION NO. 38—LUBRICATING GEARS.— See 

“Gear Lubrication,” under General Instruction No. 1, Plate 
9, Fig. 243. 

INSTRUCTION NO. 39—TO THREAD THE MECHAN¬ 
ISM— See General Instruction No. 20, with the notation that 
if there be a loop setter the film must pass under its roller, 
A, P. 10, and should just clear it when the lower loop is at its 
shortest. 

INSTRUCTION NO. 40—THE LOOP SETTER.— The 

Powers loop setter, illustrated in Plate 10, is a simple’device 
which operates well. It automatically re-sets or re-forms 
the lower loop whenever it is “lost” by reason of any one of 
the several causes which may be responsible for this very 
annoying thing. Plate 10 shows the film forming the lower 
loop around roller A. When the loop is lost (drawn taut), 
the roller is necessarily elevated, thus causing a slight ro- 


MANAGERS AND PROJECTIONISTS 


649 


tary motion in cylinder b. A diagonal slot in this cylinder, 
in contact with a pin fastened to arm C, causes the arm to 
move outward; but as arm C operates as a lever, with its 
fulcrum at point D, the other end of the arm at E moves 
inward, thus disengaging pin F from the driving pulley G. 
This breaks the connection whereby motion is transmitted 
to take-up sprocket H, and the sprocket stops revolving. 
The loop reforms instantly, and roller A is forced back into 
its original position by coil spring I. Pin F immediately 
re-engages with driving pulley G, and the take-up sprocket 
H starts to revolve again as a natural consequence. The 
whole train of operation is automatic—its results instan¬ 
taneous. 

INSTRUCTION NO. 41 —Always wipe edges of aperature 
before threading. 

INSTRUCTION NO. 42—ADJUSTING 6A TAKE-UP 
TENSION. —The take-up tension is adjusted by setting the 
collar on pulley end of spindle in or out, thus applying more 
or less pressure to the spring which holds the two halves of 
the grooved, 
split pulley to¬ 
gether. Tension 
is not regulated 
by the belt, but 
by the two 
halves of the 
pulley rubbing 
together under 
more or less 
friction, accord¬ 
ing to how much 
is supplied by 
the spring. Take 
off the belt and 
pull the two 
halves of the 
pulley apart a 

little and you Plate 10, Figure 244. 

will see how it 

works. There should be no more tension than barely enough 
to revolve the reel when it is full. Anything more is very 
hard on the film and tends to cause loss of the lower film 
loop. See General Instruction No. 22. 

















650 


HANDBOOK OF PROJECTION FOR 


INSTRUCTION NO. 43—ADJUSTING 6B TAKE-UP 
TENSION— The 6B take-up consists primarily of two fric¬ 
tion discs, which are held in contact by means of a coil 
spring. One of these discs is faced with fibre, which assures 
an excellent frictional contact. The driving disc a, Plate 11, 
is left free to revolve around take-up spindle b, as an axis. 
The driven disc c, is fastened to spindle b. By frictional 
contact, motion is transmitted from disc a, to disc c, and thus 
spindle b is caused to revolve also. The take-up reel fastens 
to spindle b at d. The reel is held firmly on the spindle by 
means of catch e. When the catch is in a horizontal posi¬ 
tion, it is in exact line with spindle b, thus making it very 
easy to put the reel on, or take it off the spindle. Spindle b 
runs in ball bearings f, which eliminate all unnecessary fric¬ 
tion in operation. 

The friction between discs a and c may be adjusted by in¬ 
creasing or decreasing the tension on spring g. This may 
be accomplished by simply giving a few turns in either 
direction to collar h, which is threaded on the end of 
spindle b. When the desired tension has been secured, the 
collar may be locked in place by means of set screw i. 

INSTRUCTION NO. 44—THE LAMP. —The lamp should 
not be allowed to become dry from lack of lubrication. It is 
next to impossible to properly handle the light using a dry 
lamp. Once a week apply sparingly a little lamp lubricant 
on all movable parts, such as threaded adjusting gears, 



Plate 11, Figure 245. 





MANAGERS AND PROJECTIONISTS 


651 


racks, sleeve rollers, etc. This lamp lubricant is. put up in 
cans by the Nicholas Power Company, Incorporated. Be 
sure and do not use too much of the lubricant, and do not 
put any on the mica insulation. You will be surprised how 
much better you can handle the light. Keep metal clean 
where carbons make contact with it. Scrape and clean thor¬ 
oughly at least once a week. Dirty carbon contacts induce 
heating and loss of power and light. Be sure the wires 
make a good electrical contact with lamp binding post. 
When terminal lugs become burned, throw them away and 
put on new ones. It does not pay to use burned lugs. When 
wires inside lamp house become burned (the life gone out 
of them) cut away the burned portion. Burned wires cause 
high resistance and loss. Unless removed, they will even¬ 
tually burn off entirely, causing vexatious delay. 

OLD STYLE 
P O W E R’S 
MOTOR 
DRIVES.— 

When using old 
style Power’s 
motor drives it 
i s important 
that you have 
the friction 
pulley in align¬ 
ment with disc 
on motor. 

When starting 
show, begin 
with slow 
speed and in¬ 
crease until 
you reach the 
required pro¬ 
jection speed. 

When motor 
drive is not in 
use, see that 

friction driving disc R-15, Plate 13, is not bearing on disc R-13, 
Plate 13. It should be free from contact. 

1. Motor should be kept free from dust, and do not allow 
oil to get into the motor windings. 

2. Belt on V pulley should not be too tight. 

3. Never put too much pressure on the adjusting screw 
























652 


HANDBOOK OF PROJECTION FOR 


R-32, Plate 12, as it flattens the driving disc R-15, Plate 13. 
If necessary, trim the leather disc just a trifle so that the 
side first touching the friction disc, when the speed lever is 
shifted over, is a trifle higher than the other side. 

4. Driving disc must be kept free from oil. 

5. Grease cups should be kept supplied with motor cup 
grease and the wicks occasionally trimmed and cleaned. 

All Power’s projector stands of the later type are drilled 
to receive Power’s speed control. When the projector is 
received, the speed control parts, as shown in Plates 12, 13 
and 14, are assembled, with the exception of the lever R-52, 



‘R-20 


but the control is not attached to the stand. All that is 
necessary to attach the control is to place same in the 
proper position, as shown in Plate P-12 and P-13, with the 
motor towards the rear end of the projector, and fasten it 
into place by means of bolts R-5 (four of them) P-13. Be 
sure that the contacts between the casting and the control 
are clean and set up bolts R-5 (four of them) tight. 

This instruction holds good with both the old style- 6A 
non-adjustable and the new style 6B adjustable stand. It is 
then necessary to attach the lever control, P-12. If it is the 
old style 6A non-adjustable stand, this lever and its casting 





























MANAGERS AND PROJECTIONISTS 


653 


is attached by means of bolts R-47 and R-48, P-12. If it is 
the new style adjustable stand, then a special bracket is sent. 
This bracket is attached to the casting by means of two 
heavy machine screws. Having attached the control lever, 
all that is necessary to complete the installation is the con¬ 
necting of lever R-52, P-12, with the end of the control lever 
at R-42, P-12, and with the bell link R-53, P-12. 

NOTE. —All parts except very small screws have the stock 
number either stamped or cast right into the part—a very 
excellent arrangement. 

All projector stands are drilled to receive the speed con¬ 



trol so that you can order same at any time and install as 
per the foregoing instructions. 

INSTRUCTION NO. 1.— The friction material R-15 is 
leather. Should it at any time develop flat spots or become 
out of round or eccentric in form, it may be trued by placing 
the point of a new 10-inch or 12-inch coarse file on rod 
R-39, P-14 (using the rod merely as a rest) and bearing 
lightly on top of friction material with motor running. 

CAUTION.—In doing this, be very careful to hold the point 
of the file perfectly flat on the rod, since if you hold it at an 















































654 


HANDBOOK OF PROJECTION FOR 


angle you will get the face of the leather ground off on a 
slant and it will then not fit the disc wheel squarely. 

INSTRUCTION NO. 2.—New friction material may be or¬ 
dered from the Nicholas Power Company, Incorporated, at 
any time. The old material may be removed by loosening 
the set screw in the hub R-16, P-14, and in set collar R-21, 
P-14, and in R-24, P-14. Having done this, R-25, P-14, may 
be pulled out to the right, thus releasing the friction wheel. 
You can then take out the old friction material by removing 
the screws in the face of R-16, P-14. The process of reas¬ 
sembling is the reversal of the process of dis-assembling, but 



Figure 249. 

Power’s Adjustable Shutter Bracket. 

these parts run on high speed, therefore, be sure and set up 
all the screws tight. 

INSTRUCTION NO. 3—CAUTION.—Never leave the con¬ 
trolling lever down when the projector is standing still; 

always pull the lever clear up so as to disengage friction 
wheel R-15, P-14, from driving disc R-13, P-14. Failure to 
attend to this matter will probably result in flat spots on the 
friction material. In nine cases out of ten where flat spots 
develop it is caused through failure to heed this warning. 











MANAGERS ANtT PROJECTIONISTS 


655 


INSTRUCTION NO. 4—TENSION. —It is, of course, nec¬ 
essary that there be sufficient tension, or friction between 
material R-15 and driving disc R-13, P-14, to drive the projec¬ 
tion mechanism, but anything more than sufficient to accom¬ 
plish this purpose will merely result in undue wear of the 
friction disc, friction material and unnecessary consumption 
of power in the motor. The tension or amount of friction 
between friction material R-15 and friction disc R-13, P-14, 
is regulated by thumb screw R-32, P-12. Proceed as follows: 

Loosen lock nut R-33, P-12, and loosen up on tension screw 
R-32, P-12, until friction material R-15 and disc R-32 are out 
of contact. Now, start your motor running and having set 
the controlling lever down so that the friction driving wheel 
is pretty well in on the friction disc, slowly tighten up on 
tension screw R-32, P-12, until the projection mechanism at- 



SPEED CONTROLA FIG. 231 
TENSION BELT TIGHTENEI 


OIL CUP 


MOTOR 
TIGHTENER 


BOLTS TO 
ATTACH TO 
PROJECTOR 


MOTOR 


FLAT MOTOR 
BELT 


PART L-H 
FIGURE 
251 

: _ : 


Figure 250. 







656 


HANDBOOK OF PROJECTION FOR 


tains full speed, and you are satisfied there is no slippage 
between the friction disc and driving wheel. Having done 
this, your tension will be just right, provided, of course, you 
have followed the instructions carefully, and have set. up 
screw R-32 just sufficient to bring the projector up to full 
speed, this being done, of course with the film in the machine, 
or in other words, under actual operating conditions. After 
the proper adjustment has been obtained, do not forget to 
tighten up lock nut R-33 tight, or else the adjustment is likely 
to work loose. 

INSTRUCTION NO. 5. —Grease cups (two of them) should 
be kept filled with some good lubricating grease (not oil, but 
grease), which may be obtained from any automobile supply 
store. The commutator of the motor may be reached by 
opening the two latticed cast-iron doors on the upper end of 
the motor. 

INSTRUCTION NO. 6. —The motor may be disengaged 
merely by removing bolts R-6, P-13, and disconnecting its 
cable. When putting the motor back, be sure and line the 



Figure 251. 


































MANAGERS AND PROJECTIONISTS 


657 


shaft of the motor directly with the friction driving shaft R-25. 
If you don’t do this, there will be trouble and probably more 
or less noise. In fact, should the device develop noise at any 
time, and you find that the friction wheel material is true, the 
next thing to look at is the alignment of these two shafts; it 
being possible that bolts R-8 worked loose and let the motor 
get out of alignment with the driving shaft R-25. 

INSTRUCTION NO. 7—NO OIL.— With the exception of 
the motor bearings, none of the other bearings of this device 
require any lubrication whatever, this by reason of the fact 
that the bushings are all of material which requires no lubri- 
caton. 

THE POWER’S ADJUSTABLE SHUTTER BRACKET.— 

This is a very simple device by means of which the revolving 
shutter may be “set” or “timed,” within certain limits, while 
the projector is running. It is illustrated in Fig. 249. The 
main advantage this device presents from the viewpoint of 
the projectionist, is that it is only necessary to set or time 
his shutter approximately correctly in the usual way, since 
he can make the finer adjustment by means of knob A after 
the projector is working. Instructions No. 28 and 32 contain 
matter concerning this bracket. 

POWER’S FRICTION TYPE, GOVERNOR-CONTROLLED 
SPEED CONTROL. —This type of speed control is illus¬ 
trated, as a detached unit, in Fig. 250. It is shown attached 
to the projector in Fig. 231. Its internal mechanism may be 
examined in Fig. 251. Fig. 250 is very largely self-explanatory. 

Examining Fig. 251, shaft M has a collar, P and Q, on 
either end, and runs in bearings N and U. All parts between 
pulley A and part B, including ball bearings F, G and O, are 
mounted upon but are in nowise attached to shaft M. By this 
we mean that they simply use shaft M as a spindle upon 
which to revolve. 

The action is as follows: The driving motor is attached 
directly to pulley A, Fig. 251, by means of an endless, flat, 
half-inch belt, as shown in Fig. 250. This pulley and part L 
form one part and revolve as a unit, part L being faced with 
a disc of friction material attached thereto by screws. 

Part B is a fork which connects directly with and is con¬ 
trolled by knob A, Fig. 231. Ball bearings F, G and O act 
entirely as thrust bearings. They are not bearings within 
the ordinary meaning of the term. Their office is to carry 
the end thrust, which is the basic principle upon which the 
control operates. 


658 


HANDBOOK OF PROJECTION FOR 


HOW IT WORKS.— When speed control knob A, Fig. 231, 
is in position to stop the projector mechanism, it has moved 
fork B away from thrust ball bearing F, and has thus relieved 
spring C of all compression. This eliminates all friction 
between discs L and H. When knob A is in position to start 
the projector mechanism, it has caused fork B to shove 
bearing F endwise, which has the effect of compressing spring 
C and bringing discs L and H together under pressure, which 
will, of course, cause part L and pulley W to revolve, and 
thus drive the projector mechanism, pulley W being a part 
of disc H. 

Understanding that pulley A and disc L are one piece, that 
pulley W and disc H are rigidly joined, and that both revolve 
freely on sha*ft M, pulley A being belted direct to the motor 
and pulley W direct to the projector mechanism, it will be 
seen that when discs L and H are pressed together by coil 
spring C, the projector mechanism will be driven by the 
friction set up between the two discs. That much is quite 
plain and simple. 

THE GOVERNOR.— And now let us examine governor T, 
Fig. 251, and see what it is for. At any given speed of projec¬ 
tion the “load” which must be pulled by the friction between 
discs L and H will require a certain, fixed amount of pressure 
by spring C to carry it. It will also be seen that exactly in 
proportion as projection speed is increased, the amount of the 
load to be pulled is increased, because increase in speed 
always requires an increase in expenditure of power. 

When the projector is started, the entire force of spring C 
will be exerted to press friction discs L and H together, and 
the amount of driving force available will depend upon how 
much the spring is compressed, which in turn depends upon 
the position of speed control knob A, Fig. 231. As soon as 
disc H starts to revolve, however, the governor also starts to 
revolve, and governor arms J, Fig. 251, are thrown outward 
by centrifugal force. If you examine these arms you will 
see their ends are hooked, and that the hooks bear upon 
collar K, against the other end of which spring C presses. It 
therefore follows that any force exerted by arms J will 
act to compress spring C, hence to lessen the friction between 
discs L and H. 

As speed is increased, the power exerted by arms J becomes 
greater, which, of course, means that they are carrying an 
increased amount of the pressure exerted by spring C, and 
in this way friction between the discs is decreased with in- 


MANAGERS AND PROJECTIONISTS 


659 


creased speed until a point is reached where there is just 
enough left to carry the load at the speed knob A, Fig. 231, 
is set for, the difference between the speed of discs L and H 
being accounted for in slippage. 

All this is very simple, lonce you understand it. We there¬ 
fore recommend that you study the foregoing carefully. 

TO DISASSEMBLE THE CONTROL.— All that is neces¬ 
sary to be done when taking the governor type speed control 
apart is to first let down the cover, which may be done by 
slipping out the latch holding it in place, and then loosen the 
set screw in collar P, slip the collar off the shaft and, holding 
the hand under the entire moving parts of the control, pull 
the shaft M out to the right, when all the parts will come 
away in the hand. When reassembling the parts great care 
should be exercised that they all be placed on the shaft in 
exactly the same position as before. The covered position of 
the various parts may be readily seen by referring to Plate 
251. 

OILING THE CONTROL. —This type of control does not 
lose its efficiency through oil coming in contact with any 
of the frictional surfaces, therefore oil may be applied to all 
parts without fear of making the control inoperative. A 
medium weight machine oil should be employed to lubricate 
all moving parts of the control, including the ball thrust 
bearings. 

Particular pains should be taken to see that screw R, Fig. 
251, is removed occasionally and oil forced into the oil hole, 
in order that the lubricant may reach the shaft M at the 
point upon which parts AL revolved. Also, as often as may 
be necessary, cup grease should be placed in oil cups S. These 
oil cups are wick oilers, and only a light grade of cup grease 
should be used. 


SUPPLY PARTS FOR NO. 6A AND 
NO. 6B MECHANISMS 
Stock—Order Parts By Number 


No. Name 

601 Main Frame 

602 Top Frame Including Thumb Screws 

603 Framing Carriage (Casting Only) 

604 Top Frame Supporting Rod (2) 

605 Stereo Support Bracket 

606 Stereo Support Bracket and Rod 

607 Stereo Collar 

608 Stereo Lens Rod 

609 Small Top Roller 

610 Small Top Roller Spindle 

611 Set Collar for Small Top Roller 

612 Top Roller Bracket 


No. Name 

613 Large Top Roller 

614 Large Top Roller Spindle 

615 Large Top Roller Bracket Spring 

616 Large Top Roller Collar 

617 Top Sprocket 

618 Top Sprocket Spindle 

619 Top Sprocket Feed Gear (large) 

620 Top Sprocket Feed Gear (small) 

621 Pinion for Automatic Shutter Spin¬ 

dle 

622 Spindle for Automatic Shutter 


060 


HANDBOOK OF PROJECTION FOR 


Stock—Order Parts By Number 


N’o. Name 

623 Friction Case Cover for Automatic 

Shutter (Outside) 

624 Friction Case Cover for Automatic 

Shutter (Inside) 

625 Friction Shoe with Spindle for Au¬ 

tomatic Shutter 

626 Friction Weight for Automatic 

Shutter 

627 Lever for Automatic Shutter 

628 Link for Automatic Shutter 

629 Apron for Top Tension 

630 Crank Shaft Driving Gear 

631 Crank Shaft 

6 32 Crank with Handle Complete 
6 33 Small Gear Meshing in Driving Gear 
634 Large Gear for Front Shutter 
6 35 Small Gear for Front Shutter 

636 Spindle for Front Shutter 

637 Bracket for Front Shutter 

638 Set Collar for Front Shutter Spin¬ 

dle (2) 

639 Lens Adjuster 

640 Large Idler Gear 

641 Large Idler Gear Spindle 

64 2 Large Idler Gear Set Collar 

643 Take-up Feed Driving Gear 

644 Take-up Feed Pulley 

645 Take-up Feed Spindle 
64 6 Take-up Feed Sprocket 

647 Framing Device Clamp 

648 Framing Device Lever Socket 

649 Framing Device Lever Socket Link 

650 Framing Device Lever 

651 Framing Device Screw 

652 Framing Device Nut 

653 Take-up Boiler Bracket 

654 Bearing for Large Idler Gear Spin¬ 

dle 

655 Take-up Boiler Spindle 

656 Set Collar for Small Spindle 

657 Take-up Boiler 

658 Take-up Boiler for Bracket Spring 

(large) 

659 Intermittent Boiler Bracket 

660 Intermittent Boiler 

661 Intermittent Boiler Bracket Spindle 

662 Intermittent Set Collar for Shaft 

663 Intermittent Spring 

664 Stud for Intermittent Boiler Bracket 

665 Take-up Boiler Bracket Spring 

666 Pin Cross and Intermittent Spindle 

667 Intermittent Siprocket 

668 Oil Tube and Cap for Large Idler 

Gear Spindle Bracket 

669 Apron Complete with Boilers 

670 Intermittent Bushing (large) 

671 Intermittent Bushing (small) 

672 Flywheel 

673 Oil Cup for Intermittent Movement 
6 74 Cover for Intermittent Movement 
675 Cam and Spindle for Intermittent 

Movement 

6 76 Collar for Intermittent Cam Spindle 
67 7 Pinion for Flywheel 

678 Toggle Joint Gear 

679 Toggle Joint' Idler Gear Spindle 


No. Name 

680 Driving Gear for Idler 

681 Driving Gear Spindle 

682 Connecting Link 

683 Small Horizontal Lever 

684 Large Sliding Guide 

685 Small Sliding Guide 

686 Stud for Horizontal Lever (2) 

687 Aperture Plate 

688 Front Plate 

689 Gate 

690 Hinge for Gate 

691 Guide Boiler (2) 

692 Guide Boiler, Bushing, Spring and 

Spindle 

693 Latch for Door 

694 Tension Shoe 

695 Gate Hinge Pin 

69 6 Cooling Plate 

697 Flap for Automatic Shutter 

698 Bock Shaft for Automatic Shutter 

699 Carriage Guide Bod (2) 

700 Outside Bevolving Shutter Blade 

701 Outside Bevolving Shutter Bushing 

(large) 

702 Outside Bevolving Shutter Bushing 

(small) 

703 Outside Bevolving Shutter Flange 

704 Stereo Support Bod 

705 Upper Film Shield 

706 Lower Film Shield 
706a Light Shield for 706 

70 7 Spindle for Lower Film Shield 

708 Lower Film Shield Bracket 

709 Flywheel Spindle Screw 

710 Upper Boiler Bracket Screw 

711 Key for Intermittent Cam Spindle 

712 Adjuster for Tension Shoe 

713 Set Collar for Carriage Guide Bod 

714 Lens Bing 

715 Tension Spring for Tension Shoe (2) 

716 Lower Film Shield Spring 

717 Spring for Friction Shoe for Auto¬ 

matic Shutter (2) 

718 Washer for Crank Shaft 

719 Take-up Boiler Flange (2) 

720 Washer for Toggle Joint Gear 

721 Latch Spring 

722 Guide for Gate Latch 

723 Screw for Framing Device Clamp (2> 

724 Screw for Top Casting on Main 

Frame (2) 

725 Screw for Bearing for Large Idler 

Gear Spindle (2) 

726 Screw in Top Casting for Stereo 

Support (2) 

726a Cap screw for Stereo supports No. 
605 and 606 

727 Screw for Fastening Large and Small 

Sliding Guides 

728 Stop Screw and Nut for Loopsetter 

729 Stop Screw and Nut for Gate 
729a Stop Stud for New Style Gate 

730 Screw for Motor Attachment on 

Frame (3) 

731 Screw for Connecting Link 


MANAGERS AND PROJECTIONISTS 


661 


Stock—Order Parts by Number 


No. Name 

732 Screw to hold cooling plate to gate 

( 2 ) 

732a Screw to set Tension on Cooling 
Plate 

733 Screw to tighten Take-up Roller 

Bracket Spindle 

734 Screw for Apron for Top Tension 

( 2 ) 

735 Screw for Aperture Plate (4) 

736 Screw for Set Collar on Top Roller 

737 Screw for Tension Spring (2) 

738 Screw for Tension Shoe Angles 

739 Screw for Outside Shutter Spindle 

Collar 

740 Screw for Friction Case Cover 

741 Stud for Framing Carriage 

742 Washer for Flywheel 

743 Screws for small and large inter¬ 

mittent bushings 670-671 (2) 

744 Screws and nuts (2) for guide cast¬ 

ing 684 

74 5 Angles for tension shoes 

746 Screw and nut for adjusting inter¬ 

mittent roller bracket 

747 Screws for gate hinge (3) 

748 Screws for lower apron (2) 

749 Screw and nut for adjusting take- 

up roller bracket 

782 Screws for upper and lower sprockets 

783 Screws and nuts for upper film 

shield (2) 

784 Screws for front plate (4) 

785 Thumb screws for top frame (2) 

786 Washers for thumb screws 785 (2) 

787 Screw to hold shutter bracket in po¬ 

sition 

788 Front screw for tightening shutter 

bracket 

789 Taper pin for crank shaft (crank 

end) 

790 Screws for outside revolving shutter 

bushing (large) (2) 

791 Screws for outside revolving flange 

(3) 

792 Screws (2) for fastening loopsetter 

bracket to frame 

793 Screws (3) for intermittent casing 

cover 

794 Spring for guide roller spindle 

795 Screws (2) for upper, intermittent 

and lower bracket springs 

796 Screws (2) “for bearing of shaft 

641 

797 Gate latch screw and nut 
79 8 Screw for lower 628 

799 Screw for crank 

MOTOR ATTACHMENT PARTS 
No. Name 

750 Main Bracket 

751 Large Shaft 

752 Small Shaft 

753 Large Gear 

754 Small Gear 

755 Pulley 

75(5 Washer for Intermediate Gear 


No. Name 

757 Intermediate Gear 

758 Washer on Main Mechanism Frame 

759 Nut on Main Mechanism Frame 

LOOPSETTER PARTS 

760 Roller Spindle 

761 Cam 

762 Pulley Gear 

763 Pin in Fork for Cam 

766 Clutch 

767 Bearing 

76 8 Fork, complete with Pin 

769 Roller 

770 Roller Washer 

771 Clutch Pin (short) 

77 2 Clutch Pin (long) 

773 Arm Spindle 

775 Stud for Bearing 

776 Clutch Pin on Fork (2) 

777 Pulley Washer 

778 Set Screw for Arm 

779 Stet Screw for Cam (2) 

780 Arm 

7 81 Tension Spring 

PARTS FOR MOTOR AND MECHANI¬ 
CAL SPEED CONTROL FOR 
NO. 6A AND NO. 6B 
CAMERAGRAPH 

Please order by number 

No. Name 

R-l Base 

R-2 Adjustable Support Bracket 
R-3 Hexagon Head Bolt for Elevation 
Block (4) 

R-4 Adjustable Support Bracket Bolt 
(4) 

R-5 Base Support Hexagon Head Bolt 
for No. 6A (4) 

R-6 Motor Support Screw Nut (4) 

R-7 Guide Rod Set Screw (8) 

R-8 Motor Support Screw (4) 

R-9 Motor Support Screw Washer (4) 
R-10 Bell Crank Stud 
R-ll Sliding Carriage Adjusting Screw 
( 2 ) 

R-l2 Controlling Lever Spring 
R-l3 Friction Disc and Shaft (not sold 
separately) 

R-l3a Hardened Pin for R-l3 

R-l 4 Friction Pulley Washer 

R-l5 Friction Pulley Driving Disc 

R-l6 Friction Pulley Hub 

R-l7 Grooved Belt Pulley 

R-l8 Sliding Carriage 

R-l9 Friction Pulley Shaft Washer 

R-20 Stop Collar 

R-21 Set Foliar 

R-22 LTniversal Flange 

R-23 Motor Shaft Coupling 

R-24 Friction Pulley Shaft Coupling 

R-25 Friction Pulley Shaft 

R-26 Controlling Lever Pivot Screw 

R-27 Bushings (4) non-oiling 

B-28 Controlling Lever Spring Shrew (2) 


662 


HANDBOOK OF PROJECTION FOR 


Stock-—Order Parts By Number 


No. Name 
R-29 Controlling Lever Pawl 
R-30 Controlling Lever Pawl Pivot Screw 
Nut 

R-31 Controlling Lever Pawl Pivot Screw 
R-32 Thrust Screw 
R-32a Hardened Pin for R-32 
R-33 Thrust Screw Lock Nut 
R-34 Controlling Lever Washer 
R-35 Bell Crank Link 
R-36 Bell Crank Screw 
R-37 Washer for Elevation Block Hexa¬ 
gon Bolt (4) 

R-38 Nut for Washer for Elevation Block 
Hexagon Bolt (4) 

R-39 Guide Rod (2) 

R-40 Lever Link Stud Washer (cotter 
pin end) 

R-41 Lever Link Nut Washer 
R-42 Lever Link for Stud Cotter Pin 
R-43 Lever Link for Stud for No. 6A 
R-44 Lever Link Stud Nut 
R-45 Lever Link Coupling Stud (Link 
End) 

R-46 Lever Link Coupling Stud (Bell 
Crank End) 

R-47 Ratchet Bolt Washer (2) 

R-48 Ratchet Bracket Bolt (2) 

R-49 Ratchet for No. 6A 

R-50 Controlling Lever 

R-51 Lever Link Coupling for No. 6A 

R-52 Lever Link for No. 6A 

R-53 Bell Crank 

R-54 Block (extension) 

R-55 Ratchet for No. 6B 

R-56 Ratchet Bracket for No. 6B 


R-57 

D. 

C. 

Motor Frame 

R-58 

D. 

C. 

Motor Armature (110 volt) 

R-58 

D. 

c. 

Motor Armature (220 volt) 

R-59 

D. 

c. 

Motor Cover with Screeen (2) 

R-60 

D. 

c. 

Motor Connector 

R-61 

D. 

c. 

Motor Hood 

R-62 

D. 

C. 

Motor Oil Cup 

R-63 

D. 

c. 

Motor Rear End Housing 

R-64 

D. 

C. 

Motor Brush 

R-65 

D. 

c. 

Motor Brush Holder (right) 


No. Name 

R-66 D. C. Motor Brush Holder (left) 
R-67 D. C. Motor Bearing 
R-68 Motor Spring 


R-69 

D. 

C. Motor Spring Wick 


It-70 

D. 

C. Motor Commutator 
volt) 

(110 

R-70 

D. 

C. Motor Commutator 
volt) 

(220 

R-71 

D. 

C. Motor Front Housing 


R-72 

A. 

C. Motor Frame 


R-76 

A. 

C. Motor Hood 


R-74 

A. 

C. Motor Oil Cup 


R-75 

A. 

C. Motor Connector 


R-76 

A. 

C. Motor Hood 


R-77 

A. 

C. Motor Rotor 



R-77c Shaft for R-77 
R-78 A. C. Motor Bearing 

R-79 A. C. Motor Spring 

R-80 A. C. Motor Spring Wick 

R-81 A. C. Starting Switch 

R-82 A. C. Starting Switch Fingers (2) 

R-83 A. C. Motor Starting Switch Pin 

( 2 ) 

R-84 A. C. Motor Starting Switch 
Spring (2) 

R-85 A. C. Motor Starting Switclj In¬ 

sulator Washer 

R-86 A. C. Motor Collector Ring 
R-87 A. C. Motor Rear End Housing 
R-88 Screw for Friction Pulley Washer- 
er (4) 

R-89 Shrew for Ratchet Bracket for No. 
6B (2) 

R-90 Base Support Hexagon Head Bolt 
for No. 6B 

R-91 Base Support Hexagon Head Bolt 
Nut 

R-92 Lever Link Coupling for No. 6B 
R-93 Lever Link Stud for No. 6B 
R-94 Check Rod for Pawl 
R-95 Lever Link for No. 6B 
R-96 Screw for Ratchet Bracket No. 6B 
( 2 ) 

R-97 Screw for Adjustable Support 

Bracket 


MUSCLE IS CHEAP. 
USE YOUR BRAINS. 



MANAGERS AND PROJECTIONISTS 


663 


The Simplex Projector 

T HE Simplex projector is made in two models, known as 
the “Regular” and the “Type S.” The only difference 
between the two is the construction and equipment of 
the lamphouse. The “Type S” is the projector herein de¬ 
scribed. The mechanism instructions for both models are 
identical. 

The Type S lamphouse is constructed of heavy Russian iron. 
The doors (one on each side) are double walled, with a half¬ 
inch air space between the walls through which a current of 
air passes constantly. The general ventilation of the lamp- 
house is excellent. 

Fig. 253 illustrates the Type S lamphouse. Its dimensions 
are: Front to back, 26 inches; width, 13.5 inches; height from 
floor to top, 27 inches. 

At the top is a vent, so arranged that connection may be 
made with a pipe leading either to the outer air or to the 
projection room vent flue. The maximum possible distance 
center of condenser can be placed from aperture is 19 inches, 
the minimum 10 inches. As shown in Fig. 253, the con¬ 
denser casing swings outward on hinges to allow the projec¬ 
tionist quick and convenient access to the lenses for clean¬ 
ing or replacing. The casing is locked rigidly in place by 
moving a single lever. Each lens is carried in a cast iron ring, 
and is retained therein by a threaded collar. These rings act 
as a heat and cold reservoir, equalizing the expansion and 
contraction of the thin edge and thick center of the lenses. 

The arrangement is an excellent one, but we would recom¬ 
mend the purchase of at least one extra ring, so that an extra 
collector lens, or even an extra collector and an extra con¬ 
verging lens, may be mounted in rings, all ready for instant 
installation in case of necessity. 

CAUTION. —When placing lenses in the rings do not screw 
the retaining collar down too tight. Leave it just a little bit 
slack, else there will be no room for expansion, and the lens 
may and probably will bind and break. The ring and the 
threaded collar are shown in lower corner of Fig. 253. 

Type S lamp is illustrated in Fig. 254. It is of rugged, 
rigid construction. It, of course, has all the necessary, usual 


664 


HANDBOOK OF PROJECTION FOR 


adjustments. The carbon jaw holders are carried by two V 2 
inch steel bars placed 3% inches apart. Between them is a 
very coarse threaded screw by means of which the carbons are 
fed together. Its pitch is such that one turn alters the distance 


51 " 



Figure 252. 












































































MANAGERS AND PROJECTIONISTS 665 

of carbon tips 3/8ths of an inch. The carbon contacts are 
one inch deep, and the clamping device is a powerful one. 
The top carbon is clamped in the jaws by a 34 inch bolt, 
and the bottom clamping bolt is inch in diameter. The 
arrangement is excellent, both by reason of size of bolts and 
because the nuts are four inches away from the arc. 

The wire terminals are something like seven inches from 
the arc and of very ample dimensions. The device by means 
of which the wire is clamped insures perfect electrical con- 



PIPE ELBOW 
-DAMPER 


TERMINAL WIRE C 
CARBON'FEE 
CARBON CLAMP 
TOP CARBON..Q 
LONGITUDINAL D 
VERTICAL C 


TRANSVERSAL i 
ENTIRE BURNE 
LOWER CARBON 
TRANSVERSAL ' 
CONDENSER ..c 
LONGITUDINAL ■ 


Figure 253. 


tact. The insulation is so arranged that there is slight danger 
of carbon dust forming grounds. The whole lamp is heavy, 
rigid and well designed. 

INSTRUCTIONS ON SIMPLEX MECHANISM 
NOTE. —While these instructions may seem complicated, 
they really are quite simple. If they are followed carefully 
and accurately the projectionist will have little trouble in 
their successful application.. “P.I, “P.5,” etc., means Plate I, 
Plate 5, etc. Reference to general instructions means the 
instructions beginning on Page 592, which apply to all pro¬ 
jectors alike. 

INSTRUCTION NO. 1. TO REMOVE FILM TRAP GATE, 
OR DOOR, A, P 2 .—First shove knob S-134-E, P.2, in as far 
as it will go, which places gate or door in position shown in 








666 


HANDBOOK OF PROJECTION FOR 


P.2. Next lift up on gate, which should readily disengage 
from its holding pins. If it sticks so you cannot move it, set 
a stick of hardwood against its lower outside corner and tap 
gently with a hammer until it starts, whereupon it may be 
lifted out. 

CAUTION. —Attached to lower end of gate or doors is the 
shoe or cradle which acts as idler to the intermittent sprocket. 
Under no circumstances apply pressure to this in an attempt 
to disengage the door or gate. If you do you may and prob¬ 
ably will bend it, which means trouble. See Instruction No. 
31. 

INSTRUCTION NO. 2—TO REMOVE INTERMITTENT 
MOVEMENT COMPLETE AS A UNIT.— First remove 
knurled screw S-209-G, P.3, and pull the gear it holds in 
place off its spindle. Pull curved part of mechanism casing 
cover D-9, P.6, down, and lay a weight on it to keep it down 
out of the way. Open gates or door by pushing knob 
S-134-E, P.2, inward, thus preventing its interference with 
intermittent sprocket when you pull unit out. Loosen retain- 



Figure 254. 






MANAGERS AND PROJECTIONISTS 


667 


ing screws S-157-B, P.2, (two of them) and shove locking ears 
they hold aside so they no longer engage with holding ring. 
Turn flywheel until set screw in collar C-192-G, P.2, faces 
lamphouse, then loosen screw and take collar off shaft. You 
may now pull the entire intermittent unit (which includes 
flywheel, intermittent oil casing and intermittent sprocket), 
together with gear G-133-G, P.3, out on the flywheel side, 
grasping flywheel with right hand and gear with the left. 

INSTRUCTION NO. 3—TO REPLACE INTERMITTENT 
UNIT. —This requires very careful work and an exact follow¬ 
ing of the instructions supplied. The operation is simple 
enough, but due to the fact that the intermittent casing must, 
in the very nature of things, fit into its holding ring accurate¬ 
ly, it is quite possible to, by carelessness, or even by a com¬ 
paratively slight error in procedure, do very serious damage 
to the parts. We therefore advise you to study the instruc¬ 
tions carefully, and to follow them exactly. 


W-I26- 
R-5 
OIL 
S-5I2-B 
C-IOOA 
S-34IG 
N-II9-G 

S-II5 A- 

B-I98-A 


K-I02-A 
S-324-D 
S-I92-D 
S-337-E 
S-292-E 
R-I30-E 
SI6I-E 
E-l 



Plate I, Figure 255. 













668 


HANDBOOK OF PROJECTION FOR 


Hold intermittent unit in your right hand, by its flywheel. 
Mesh teeth of gear G-133-G, P.3, with teeth of small gear at¬ 
tached to inner surface of flywheel and, holding large gear in 
left hand, shove intermittent casing into opening A-7, P.4, 
at the same time entering shaft (S-444-G, P.4) of large gear 
into its bearing. Shove both gear and casing into place at 
one and the same time, being very sure dowel pin on framing 
can engages properly with hole in intermittent casing. 

TAKE NOTICE. —It is essential to smooth running that the 
teeth of gear G-133-G, P.3 and the small gear it meshes with 
on flywheel shaft, be in the same relation to each other they 
were before they were separated. In other words the same 
teeth must be engaged that were engaged before disassembled. 
On outer rim of the large gear you will find stamped a 
cipher (0), and another on the rim of the flywheel, unless you 
have an old model mechanism, in which case you should turn 



Plate 2, Figure 256. 

















MANAGERS AND PROJECTIONISTS 669 

flywheel until large end of pin in hub of gear on vertical shaft 
just under governor weights points straight out, and make a 
scratch mark on rim of large gear exactly opposite end of 
pin and another at edge of flywheel. 

After intermittent unit and gear are in place pull intermit¬ 
tent casing out just far enough so that the two gears disen¬ 
gaged, and if the 0’s are present, turn gear and flywheel 
until the “0” on each is in line with the other, whereupon 
mesh the gears. Then pull both gear and casing out until 
large gear disengages from gear on vertical shaft. You now 
have gear G-133-G, P.3 meshed with gear on flywheel shaft 
correctly, but not engaged with gear on vertical shaft, which 
is the second gear below governor weights on the shaft. 

Turn flywheel and gear G-133-G until the “0” is exactly 
opposite center of vertical shaft, and turn vertical shaft until 
big end of pin is opposite the “0”, whereupon shove the 
casing and gear home, put collar on opposite end of shaft of 
gear G-133-G, replace gear G-112-G, P.3, and its retaining 
screw, being very sure the clutch faces on shaft of gear 
G-112-G, P.3, engage properly. 

NOTICE. —Unless these clutch faces or shoulders do engage 
properly, the gear will not go clear on and the teeth of the 
two gears will not engage their full width 

Next engage locks L-116-B, P.2, (two of them) with rim or 
flange of framing cam, tighten their holding screws and the 
job is done. 

INSTRUCTION NO. 4—ADJUSTMENT TO ELIMINATE 
LOST MOTION IN INTERMITTENT SPROCKET.—See 
general instruction No. 5, and study it. Remember that this 
adjustment is usually made when the mechanism is cold, and 
that the parts will expand through the normal heat of opera¬ 
tion, which includes some heat from the “spot,” which is 
carried through the metal. Therefore always make the test 
for lost motion in the intermittent sprocket immediately after 
running a reel. 

First turn flywheel until intermittent sprocket stops, and 
then about a quarter of a turn more. You then know the 
movement or the star is “on the lock,” as it must be for this 
adjustment. In the hub of the intermittent casing, B, P.2 
or B-8, P.4, you will find two small screws. Loosen, but do 
not remove them, after which apply wrench end of Simplex 
spanner wrench, or some other suitable wrench to the hexa¬ 
gon nut between the intermittent sprocket and the bushing. 


670 


HANDBOOK OF PROJECTION FOR 


Turn this nut, which is a part of the bushing, one way or the 
other until excess circumferential play of sprocket is elim¬ 
inated. When through, tighten the holding screws in the hub 
and the job is done, but be very careful as to the latter, as 
the screws have a tendency to clamp the star against the cam, 
in which case the adjustment made must be slacked off just 
a little bit. Be sure this does not happen. You can test it by 
trying the flywheel very gently. If it refuses to turn, or turns 
hard, then loosen the screws and slack off on the adjustment 
just a little. 

CAUTION.—Do not get the movement too tight. There 

should be no lost motion in the sprocket, but at the same time 
the flywheel should turn freely. Before making adjustment, 
if the projector has been standing still for some time first 
run it a little to get the parts thoroughly covered with oil. 

INSTRUCTION NO. 5—REMOVING AND REPLACING 
INTERMITTENT SPROCKET.—We do not advise you to 



A-131 
S-494-A 
S-446G 


C-I93-C 
W-I05-G 
OIL 
L- 

G-I33-G 

G-I34-G 


189-A 
B-I27-A 
S-5I4-C 
-G 


S-454B 

S-5I2-B 


S-I42-G 


S-222G 


-II5-G 


L-I07-G 


Plate 3, Figure 257. 








MANAGERS AND PROJECTIONISTS 


671 


attempt this, unless conditions compel you to do it. We 
strongly advise that you purchase an extra intermittent unit, 
and that when repairs are necessary you install the spare and 
ship the other to the factory, or to a Simplex distributor for 
expert attention. 

Granted the removal and replacement of an intermittent 
sprocket is a simple operation, still it is one demanding such 
extreme accuracy that it is best done at the factory. 

To remove intermittent sprocket, first follow instruction No. 
2 and loosen the two screws, B, P.2, as for adjusting star and 
cam, being sure you have them backed off enough to release. 
You may then, by exerting reasonable force, pull the intermit¬ 
tent sprocket, its shaft, the bushing and the star straight out 
of the oil casing. To remove sprocket and install a new one 
see Section C, General Instruction No. 5. 

When sprocket is in place on shaft, insert star, bushing, 
etc., in casing, being very certain that star and cam engage 
properly, and tighten the two holding screws. To replace 
intermittent movement unit, see General Instruction No. 2. 
You will probably have to re-set the revolving shutter; see 
Instruction No. 36. 

INSTRUCTION NO. 6—END PLAY IN INTERMITTENT 
SPROCKET. —While a very small amount of end play or 
end movement of intermittent sprocket may do no harm, still 
there should be none at all. If objectionable end play should 
develop, which you are unable to trace to any other source, 
examine the pins which fasten the sprocket to its shaft. It 
is possible the holes in the sprocket hub have become worn 
out of oval or egg-shape, in which case the sprocket would 
have lateral motion equal to the amount of the wear. You 
can test this by the feel and by examining with a magnifying 
glass, such as a good reading glass. A condenser lens for a 
magnifier will hardly serve for this, though you might try it. 

If you find the hole to be out of round, then secure from a 
Simplex distributor, or from the factory, a suitable reamer 
and, removing the sprocket by following Instruction No. 5 in 
the 'matter of taking out the sprocket unit, and using the 
anvil illustrated in Fig. 225, drive out the pin and ream out 
the hole in sprocket hub and shaft, being careful to ream out 
only just sufficient metal to make the hole round. You may 
then drive in two new pins and reassemble the parts. 

INSTRUCTION NO. 7—REMOVING INTERMITTENT 
OIL WELL CASING COVER.— To remove this part, D, P.2 


672 


HANDBOOK OF PROJECTION FOR 


and B-8, P.4, proceed as follows: First follow instructions 
No. 2 and 5. In the hub of the casing cover you will find a 
hole made to receive the pin of the Simplex spanner wrench. 
By holding the casing stationary and using this wrench you 
may unscrew the cover, which has an ordinary right-hand 
thread. 

NOTE. —It will be necessary to tap the wrench gently with 
a small hammer in order to start the part, but remember when 
doing this that you are working with finely finished parts, 
made with extreme accuracy, therefore use a little common 
sense and do not abuse them. 

INSTRUCTION NO. 8—REMOVING CAM OF INTER- 
MITTENT MOVEMENT, B-16, P.5. —First follow instructions 
Nos. 1, 2 and 7. Next remove collar on end of shaft carrying 
the cam, whereupon you may pull the cam out, together with 
its shaft and gear. 

INSTRUCTION NO. 9—TO REMOVE FLYWHEEL 
SHAFT, S-454-B, P.3. —First follow instructions Nos. 7 and 8, 
then loosen set screw in hub of flywheel and pull flywheel 
and the gear attached to its inner surface off the shaft. The 
shaft will then drop out of its bearing through the oil well. 

INSTRUCTION NO. 10—REMOVING COMPLETE FIRE 
SHUTTER GOVERNOR UNIT.— The fire shutter governor, 
W-126-D, P.3, the vertical shaft on which it is mounted, and 
the gears on the shaft are for all practical purposes one unit. 
To remove any one of the parts it is necessary to do consid¬ 
erable in the way of preparation. First take off the upper 
magazine and remove screws which hold top plate of me¬ 
chanism casing. Next loosen set-screw S-125-A, P.2, and lift 
off focusing knob K-119-A, P.2. Remove left door link screw 
and lift off top plate of mechanism casing. 

Next follow Instruction No. 2, and then, using a small steel 
punch, being sure to drive from the small end of the pin, 
drive out taper pin (it will be a set-screw if you have an old 
model mechanism) in hub of gear G-120-G, P.4, which is the 
first gear below the governor weights. Next drive pin out 
of hub in next gear below. Remove center set screw from 
upper link holder H-121-G, P.3, which will be a taper pin in¬ 
stead of a set-screw if your projector be an old model. 

If you have followed these instructions correctly you have 
now released all parts mounted on vertical shaft, below its 
upper bearing, from the shaft and you may now lift the shaft 
out. Should the shaft stick, line the jaws of a plier with 


MANAGERS AND PROJECTIONISTS 


673 


heavy paper or thin sheet copper and, grasping upper end 
of shaft, using center wall of frame as a fulcrum, start the 
shaft by prying. 

INSTRUCTION NO. II—TO REMOVE SLIDING GEAR 
G-116-G, P.4. —This is just under the long gear on revolving 
shutter shaft, and which slides back and forth when framing. 
First follow Instruction No. 10. You may then remove both 
gear and shaft by loosening set-screw in collar C-193-G, P.3, 
pn outer end of shaft, and pulling shaft out to the right. 

INSTRUCTION NO. 12—REMOVING GEAR ON RE¬ 
VOLVING SHUTTER SHAFT.— To remove this gear, G- 
147-G, P.4, loosen set-screw in back end of gear and pull the 
shutter shaft out. Old model mechanisms have taper pin in¬ 
stead of set-screw. Next remove link screw of casing door 
and take out upper and lower screws holding left side of 




OIL 
G-I47- 
G-ll 
GII5-G 
D-13 


WI3I-B 
B-4 
B-8 
B'l 
G-l 

WI52-B 

CI26-A 

P-I96-A 

S-II8-A 


S-I4I-D 
i-G 
G 

S-I33-C 
L-l I l-C 

s-ioi*c 

L-IIO-C 
-C 
D-2 


20-G 
P-I07-G 

A-7 
G-l 1 i-G 


122* G 


Plate 4, Figure 258. 






674 


HANDBOOK OF PROJECTION FOR 


front mechanism casing, C-152-D, P.6. Remove this part and 
gear is released. 

INSTRUCTION NO. 13—REMOVING REVOLVING 
SHUTTER BRACKET. —To remove this bracket, which car¬ 
ries revolving shutter gears and shaft, first follow Instructions 
Nos. 10, 11 and 12. Next remove washer and screw holding 
framing lever spring S-330-G, P.3, using extreme care in so 
doing, as the spring is under tension and is a very powerful 
one. Keep hands away when removing the screw and washer, 
then apply blade of screw-driver to back side (side next lamp- 
house) of end of spring which points toward base. Push out¬ 
ward (toward screen and the spring will release and unwind 
Jtself, probably with startling suddenness (which will do no 
harm), whereupon it may be removed with perfect safety. 
Provided your mechanism be a late model, you will find a 
hole in front mechanism cover opposite center wall of frame 
of mechanism, just over a set-screw. Loosen this set-screw, 
which will release the stud holding framing slide lever L-104- 
G, P.3, and pulling stud out will release the lever. If mech¬ 
anism be an old model and there is no hole by means of 
which you can reach the set-screw, we would advise you to, 
using a breast drill and a half-inch drill, make a hole, since 
otherwise you must remove the entire right hand front 
mechanism cover. Having removed framing slide lever 
L-104-G, P.3, you have now only to remove the screws (two of 
them) holding bracket to frame to release the bracket. 

INSTRUCTION NO. 14—REMOVING REVOLVING 
SHUTTER SHAFT.— To remove the revolving shutter shaft, 
S-574-G, P.2, it is only necessary to take out set-screw in 
rear end of hub, G-147-G, P.4. This screw is quite short and 
has a pointed end which engages with counter sunk hole in 
shaft. Better (using a small, magnetized screw-driver, if you 
have one), remove it entirely, but be sure you do not lose it. 

INSTRUCTION NO. 15—REMOVING REVOLVING 
SHUTTER BLADE. —To remove revolving shutter blade 
from its hub (a very necessary operation in many circum¬ 
stances), take out ten screws from shutter hub, if old model 
projector or shutter; or five screws, if late model. This re¬ 
leases blade from spider. In replacing, be sure the word 
’ Simplex” (old style shutter), or the words, “Extralite Cut¬ 
off Blade,” is directly in line with the heads of set-screws 
S-165-D, P.3. 

INSTRUCTION NO. 16—TO REMOVE SHUTTER AD- 

JSTING SLIDE BLOCK S-323-A, P.2. —First follow Instruc- 


MANAGERS AND PROJECTIONISTS 


675 


tion No. 2, and parts of Instruction No. 13, afterward remov¬ 
ing mechanism casing parts C-157-C, C-152-D and C-159-C, 
all P.6. Next take off top plate, P-207-D, P.6, of mechanism 
casing. Remove link screw S-181-D, P.6, and take out the 
framing slide lever as per instruction No. 13. Next drive out 
the stop pin near upper surface of lower track the block slides 
on. Loosen set-screw S-253-A. P.2, and turn shutter adjust¬ 
ing knob K-120-A, P.2, counter clockwise until it disengages 
from the block, whereupon you may pull the block out. 

INSTRUCTION NO. 17.—TO REPLACE FRAMING SLIDE 
LEVER. —In Instruction No. 13 you were given directions for 
removing framing slide lever L-104-G, P. 3. Assuming that 
gear G-112-G, P.2, gear G-133-G, P.3, and the flywheel have 
been removed (see Instructions. 2 and 9 for their removal), 
first place upper, forked end of framing slide lever in the 
slot on under side of casting which carries sliding gear G- 
116-G, P.4, so that the fork engages with block in framing 
slide. The lever itself is bow-shaped, and the outward bow 
must be forward—toward the screen. Next shove the stud 



Plate 5, Figure 259. 

















676 


HANDBOOK OF PROJECTION FOR 


which holds the lever into place, being certain that set¬ 
screw S-223-G, P.2, engages with countersink in shank of 
stud. Screw set-screw down tight. Place coil spring on stud 
with the hook upward and toward the lever. Engage the 
hook with lever. Put washer and screw on end of stud but 
do not tighten screw down. Leave it quite slack. 

In the end of the stud you will have noted a groove. This 
is to hold the spring when under tension. With the screw 
slack enough so you can do it, grasp the end of the spring 
which hangs downward and force it around to the right 
(clockwise) until it has made approximately one full revolu¬ 
tion and points straight downward, whereupon snap it into the 
groove in end of stud. Hold the spring in this position and 
tighten the screw in end of stud down solid. 

INSTRUCTION NO. 18.—REMOVING SHUTTER AD¬ 
JUSTING KNOB AND SHAFT K-120-A, P.2— Remove 

screw and washer which hold lower sprocket idler bracket to 
its shaft, or stud. Raise bracket away from sprocket and pull 
it off. Next loosen nuts which are locked together on 
threaded portion of shaft and, holding the nuts stationary, 
turn knob K-120-A, P.2, counter clockwise until it releases 
from sliding block and lock nuts. You may then pull it out. 

INSTRUCTION NO. 19.—TO REMOVE FRAMING CAM.— 
This is the part the framing lever link, L-114-G, P.2, connects 
to. It is numbered C-100-A, P.l. To remove it, first follow In¬ 
struction No. 2. Next remove screw S-223-G, P.3, which con¬ 
nects upper end of link to cam. Take out screws holding 
back mechanism casing cover, C-151-D, P.6, and remove same. 
With thumb of left hand shove framing slide lever, L-104-G, 
P.3, forward (toward screen) as far as it will go and insert 
a piece of wood about one inch thick between sliding gear, 
which is under large gear on main shutter shaft, and its 
bracket, to hold the gear and lever forward where you shoved 
them. A smaller piece between the lever and its stop will 
serve as well. The idea is to hold the lever where you shoved 
it, which relieves pressure of framing slide lever spring, act¬ 
ing through tension block, from edge of cam we are to re¬ 
move. 

Next, using a long, slender-bladed screw-driver, loosen set¬ 
screw in framing cam adjusting ring, R-133-A, P.l. This screw 
locks together the ends of the ring where they are cut. Its 
loosening unlocks the ring, which may be unscrewed and the 
framing cam worked slowly around until it is free, when it 
may be pulled out to the left. 


MANAGERS AND PROJECTIONISTS 


677 


To replace this cam is merely the process before described 
in reverse, but attention must be given the matter of tighten¬ 
ing ring R-133-A, P.1, which must be screwed in far enough 
to eliminate any possibility of lost motion between the casing 
and its holding ring, but not tight enough to cause binding 
during the process of framing the picture. 

INSTRUCTION NO. 20.—REMOVING AUTOMATIC FIRE 
SHUTTER E-7, P.l. —Unscrew the stud with which you raise 
the shutter, S-514-C, P.3. Remove lever screw, S-100-E, P.l, 
which is immediately over knob S-134-E, P.2, with which the 
gate is shoved open, and screw S-102, P.l. When this latter 
screw is out the fire shutter will drop down and the lever may 
be pulled out to the right. 

NOTE. —If it be an old type mechanism there will be a 
set-screw instead of the lifting stud, which may be removed 
after taking off C-151-D, P.6. 

INSTRUCTION NO. 21.—TO REMOVE AUTOMATIC FIRE 
SHUTTER S-316-E, P.l. —Remove link retaining screw 
S-102-E, P.l, which is the screw by means of which the link 
at top of shutter attaches to lifting lever. Next remove entire 
lateral guide roller unit, as per Instruction No. 22, whereupon 
you may lift the shutter out. 

INSTRUCTION NO. 22. TO REMOVE LATERAL GUIDE 
ROLLER UNIT S-292-E, P.l. —To remove this or any one of 
its parts, loosen the set screw in its left hand hub and the 
screw in collar at opposite end. You may then pull shaft 
out to right, starting it out by prying against its left hand end 
with a screw-driver blade. The removal of the shaft releases 
all the parts. 

CAUTION. —Before disturbing the unit examine it carefully 
and be sure you understand how the parts go. There are six 
of them, viz: a shaft, collar, spacing bushing, two rollers and 
a coil spring. This guide helps in holding the film central 
over aperture, hence disturbing the position of any of its 
parts would have a serious effect. 

INSTRUCTION NO. 23.—TO REMOVE GOVERNOR LIFT 
LEVER D-2, P.4. —It is only necessary to take out the screw 
in its right hand end, which joins it to the vertical link, and 
the fulcrum screw S-150-D, P.4. You may then lift the part 
away. 

INSTRUCTION NO. 24.—TO REMOVE FRAMING SLIDE 
LEVER L-104-G, P.3. —See Instructions Nos. 13 and 17. 


678 


HANDBOOK OF PROJECTION FOR 


INSTRUCTION NO. 25.—TO REMOVE AND REPLACE 
SPRING MOUNTED ON FRAMING SLIDE LEVER L-104-G, 
P.3. —See Intructions Nos. 13 and 17. 

INSTRUCTION NO. 26.—TO ADJUST FRAMING TEN¬ 
SION. —If the framing handle shows tendency to work up or 
“creep,” there is not sufficient tension. If the framing handle 
works unduly hard or sticks, the probable trouble is too 
much tension. Proceed as follows: Remove screw S-209-G, 
P.3, and pull the large gear it holds off its spindle. Just to 
the right of and below the spindle you will see a stud on the 



S-I8I-D 
L-II3-D 
C-I52-D 
C-II8-D 
S-I92-D 
D-18 
G-I24-D 
7 

C-I59-C 

C-II8-D 
6 

65 C 
C-I57-C 
R-I6I-C 
R-I60C 
S-485C 


S-I78-D 
C-I5I-D 
D-19 
D-12 
D-8 
5‘361-D 
S-J85-D 
D-9 


E* 

B-I98-A 
P-207-D 
C-8 


Plate 6, Figure 260. 


end of which is two hexagon nuts. Behind these nuts is the 
coil spring which provides tension for the framing device. 
Loosen the outer nut, which is merely a lock nut, and tighten 
or loosen the inside nut until the framing handle works to 
suit you, after which tighten lock nut again. The nuts are 
on stud P-196-A, P.4, and the spring is numbered S-341-G, P.l. 

INSTRUCTION NO. 27.—TO REMOVE FRAMER TEN¬ 
SION SPRING S-34I-G, P.l. —First follow Instruction No. 
26, only instead of merely loosening the nuts, remove them 
entirely and pull the spring off. 

CAUTION.— In reassembling be sure and place washer at 
either end of spring. 





MANAGERS AND PROJECTIONISTS 


679 


INSTRUCTION NO. 28.—REMOVING FILM TRAP COM¬ 
PLETE. —Should it ever become necessary to remove the 
entire film trap assemblage, E-l, P.1, as a unit, it may be 
done by taking out the two large screws S-133-C, P.4, and 
S-514-C, P.3, which releases the whole thing, but it is best 
to first remove the door, as per Instruction No. 1, to avoid 
possibility of damage to intermittent sprocket. 

In reassembling it is absolutely necessary that the unit be 
accurately placed and lined, else the aperture will not be 
square with the lens. Have the engaging surfaces perfectly 
clean. Place the part in position engaging it with the 
locating pins and starting the two holding screws, tightening 
them down, but not solidly. Next (IMPORTANT), with 
the gate shoved back (open), place a straight-edge of metal, 
such as a machinist’s six inch rule (scale) on the film track, 
or “trap shoe” as the Simplex folks call it, letting the 
straight-edge project down past the sprocket. If the part is 
in line when the straight-edge lies flat on the film track, it 
will just touch the face of the intermittent sprocket. If the 
rule rests on sprocket face and is held away from lower end 
of film track, or if it rests on track but does not touch face 
of sprocket, tap casting forward or back until track and 
sprocket face are exactly in line. When this is done, tighten 
up the two holding screws tight. 

INSTRUCTION NO. 29.—TO REMOVE FILM TRAP STUD 
S-134-E, P 2 .—This is the thing you shove the gate, or door, 
open with. To remove it is a simple matter. The knurled 
knob at its end looks like it is one with the nickeled stud, but 
it is not. What seems to be a nickeled stud extending into the 
casting is only a thimble of thin metal covering the steel 
stud beneath. It is held by the knurled knob. Wrap the 
knurled knob with either cloth or paper, to prevent marring 
its surface, and grasping it with a gas plyer unscrew it. It is 
an ordinary right hand thread. It holds a light, rather long 
coil spring under compression. The spring is between the 
nickeled thimble and the stud. Having removed the screw, 
take off the thimble and spring. You must next follow in¬ 
struction No. 28 (or you may do this first), after which the 
stud and entire gate will be released. To reassemble, note 
reassembling instruction under Instruction No. 28. 

INSTRUCTION NO. 30.—REPLACEMENT OF FILM 
TRACK SHOES. —Film track shoes, S^309-E, P.S, are subject 
to very heavy wear, and as soon as there is appreciable wear 
they should be removed and replaced with new ones, other- 


680 


HANDBOOK OF PROJECTION FOR 


wise there will very likely be an out-of-focus effect visible 
from time to time on the screen. 

The old type shoes are fitted with beveled edges which 
slide into a slotted groove in the film trap. To remove, first 
follow Instruction No. 2, then take out screw holding its 
upper end, one of which is shown at S-432-E, P.l. Remove guide 
rollers, as per Instruction No. 22. Remove entire intermittent 
unit as per Instruction No. 2. This latter is necessary because 
the part will not slide down past the intermittent sprocket. 
You may now slide the shoe down and out. The process of 
reassembling is merely a reversal of the foregoing. 

Shoes of late design have four wearing edges. When worn 
they should shift from right to left, and vice versa. They 
may then be reversed and the back sides used in the same 
way. These shoes are released by taking out three small 
screws, S-432-E, P.l, the heads of which are on front of heat 
shield, or cooling plate E-5, P.l. 

CAUTION. —When installing a new shoe be sure the ends 
of the screws do not extend through the shoe or protrude 
on the wearing side. This is especially to be guarded against 
if the same screws removed from the old shoes are used. If 
they do, the end may be dressed down, using a very fine file, 
but great care must be exercised not to mar the guide rollers 
which protrude through the shoes near their top. It may even 
be well to, as a matter of precaution, remove the guide rollers, 
as per Instruction No. 22. 

INSTRUCTION NO. 31.—INTERMITTENT SPROCKET 
IDLER SHOES. —The film is held to the intermittent sprocket 
by a cradle shoe, held in a steel apron attached to film trap 
gate, or door. This shoe performs the same office for the in¬ 
termittent sprocket that the sprocket idlers perform for the 
other sprockets. The adjustment of the shoe or cradle is of 
great importance. Examine part C, P.2, and see exactly how 
it works. Note that the cradle held in the steel apron 
attached to lower end of gate, or door, is held in place by a 
flat spring which allows it to adjust itself to the surface of 
the sprocket, and to move back when a thick splice or a 
stiff splice goes through. 

Note also that the adjustment must be made by observing 
the relation of the outer tracks of the shoe to the face of the 
sprocket. The adjustment should be such as will hold the 
film firmly to the sprocket, without undue friction, at the 
same time allowing sufficient movement to allow a stiff or 


MANAGERS AND PROJECTIONISTS 


681 


thick splice to go through without trouble. In figures the 
adjustment should be such that when the gate or door is 
closed the cradle shoe will fit the curvature of the sprocket, 
and so that the shoe will push back about 1 /64th of an inch 
away from the sprocket face, which is about the thickness of 
an ordinary business card. 

The maintenance of this adjustment is of great importance. 

It is difficult to tell you just how to obtain it, since it must 
be done by bending the apron. It is largely a matter of 
knowing just what is needed (which we have told you) and 
exercising plain common sense. 

INSTRUCTION NO. 32. —REMOVING PROJECTION 
LENS HOLDER. —Projection lens holder, A-4, P.2, may be 
removed by taking off the front mechanism casing cover 
C-159, P.6, and removing screw S-494-A, P.3. The whole tube 
and sliding block which carries it may then be pulled out. 

To adjust lens in holder first loosen clamp screw at front 
end of top of lens holder. There are several adapters, or 
bushings which fit inside the holder to reduce its diameter to 
accommodate various diameter lens tubes. Insert the proper 
adapter, according to the diameter of your lens tube. Strike 
the arc, and, without any film in, open the automatic fire 
shutter and block it open. Project the white light to screen. 
By means of focusing knob rod R-178-A, P.2, on top of 
mechanism, set lens holder at center of its travel. Then 
shove lens tube in or out until edges of light on screen are 
sharply focused, whereupon tighten clamp screw S-165-A, P.2, 
on top of lens holder. Final focusing will then, of course, 
be completed with focusing screw after picture is being 
projected. 

NOTE. —When position of lens in holder has been finally 
fixed, make a scratch mark on lens tube barrel at front end of 
holder, so that when you for any cause remove the lens it 
may be correctly replaced by properly locating the mark. 

INSTRUCTION NO. 33.—ADJUSTING UPPER AND 
LOWER SPROCKET IDLER ROLLERS.— The distance of 
idler rollers from' spocket is determined by the adjustment of 
screws in idler roller brackets, S-194-C and N-115-C, P.5. See 
General Instruction No. 12. 

INSTRUCTION NO. 34.—TO REMOVE UPPER SPROC¬ 
KET IDLER BRACKET TENSION SPRING, S-570-C, P.2.— 

You may either remove the entire film trap, as per Instruc¬ 
tion No. 28, or move the top plate of the mechanism casing 


682 


HANDBOOK OF PROJECTION FOR 


and either make a special tool or secure an offset screw¬ 
driver for taking out the two screws at upper end of spring. 
The spring is the flat steel spring which extends down from 
the casting which forms the bearing for the upper sprocket 
shaft. Its lower end curves and engages the end of the idler 

bracket arm. The 
two holding screws 
are right opposite 
the end of the upper 
sprocket. 

To replace this 
spring close the 
idler up against the 
sprocket and be sure 
you tighten the hold¬ 
ing screws down 
solidly. 

INSTRUCTION 
NO. 35.—T O RE¬ 
MOVE THE LOW¬ 
ER SPROCKET 
IDLER BRACKET 
SPRING.— It is only 
necessary to remove 
one screw. The 
spring engages with 
the casting forming 
the bearing of the 
main crank shaft. 
You cannot see the 
screw when the mechanism casing is in place, but you can 
feel it. You make take off front casing C-159-C to get at the 
screw, but by exercising a bit of patience you can remove and 
replace it, if you make a special screw-driver by breaking off 
an inch of an old hack-saw blade and grinding one end to a 
point, or (better) you may secure an offset screw-driver from 
Simplex distributor. In replacing the screw be sure you set 
it up tight. 

INSTRUCTION NO. 36.—SETTING THE REVOLVING 
SHUTTER. —See General Instruction No. 22. The blade 
stamped “Simplex,” or in the case of the Extralite, “Extralite 
Cutoff Blade” is the master blade. General Instruction No. 22 
will inform you fully as to the principle involved in shutter 
setting. Having studied general instruction thoroughly, so as 



Figure 261. 










MANAGERS AND PROJECTIONISTS 


683 


to get a good idea of exactly what it is you wi$h to accom¬ 
plish, place framing lever C-ll, P.2, in central position, and 
by means of knob K-120-A, P.2, set sliding block S-323-A, P.2, 
in the center of its travel, which is midway between the two 
stop pins in its lower track. Next loosen the set screws which 
hold the shutter hub to the shaft just enough so you can pull 
the shutter around by exerting a little force. 

Next place a finger of one hand on the intermittent sprocket 
and turn the flywheel IN THE DIRECTION IT NORMALLY 
RUNS until a point is reached where the intermittent sprocket 
just barely begins to move. Move the flywheel back and 
forth until you determine exactly the point where it starts 
the sprocket. Now hold the flywheel absolutely stationary 
and revolve the shutter on its shaft in the direction it 
normally runs, until the edge of the master is about three- 
fourths across the lens, which should be right. 

Now turn the flywheel VERY SLOWLY in the direction it 
runs, until the point is exactly reached where the intermittent 
sprocket ceases to move. If the other edge of the master 
blade now covers as much of the lens as the other edge did, 
then the shutter is correctly set. If not, then equalize the 
two edges as to lens covering, and see instructions for adjust¬ 
ing revolving shutter to local conditions under General In¬ 
struction No. 22. When the job is done and a slight travel 
ghost shows up or down, but only one way, this may be 
eliminated by slightly altering shutter adjustment by means 
of knob K-120-A, P.2. 

The shutter setting device is operated by knob K-120-A, P.2. 
It is for the purpose of adjusting the revolving shutter to 
correct any slight error in timing. The shutter must, however, 
be first correctly set as per the foregoing instructions. 

INSTRUCTION NO. 37.—ADJUSTING GATE TENSION.— 
See General Instruction No. 9. Correct tension is that 
pressure which will cause film to begin to overshoot (picture 
to move up on the screen) when a speed ten revolutions ot 
the crank shaft in excess of your highest projection speed is 
reached. Anything in excess of this is very bad for both 
the film and the projector mechanism. To change tension on 
the Simplex it is necessary to bend the spring which supplies 
pressure to the tension shoes. This is a curved flat spring, the 
upper end of which is seen protruding through a slot in the 
upper side of the lens barrel extension which attaches to the 
gate or door. It is attached to the door by means of two 
screws, the removal of which allows it to be lifted out. A 
/nagnetized screw-driver should be used for this job. A 


684 


HANDBOOK OF PROJECTION FOR 


door should first be lifted off, as per Instruction No. 1. The 
springs should be bent without removing, but be very sure you 
bend both sides alike. 

INSTRUCTION NO. 38. —The Simplex folks supply, on 
order, an undersize aperture to be used where it is neces¬ 
sary to eliminate keystone effect by filing. This aperture is 
about 1/32 of an inch less in size than the regular aperture 
opening. 

INSTRUCTION NO. 39.—TO REMOVE APERTURE 
PLATE.— To remove aperture plate follow instruction 30, 
since film tracks must be taken out, then remove projection 



Figure 262. 


lens tube by loosening clamp screw S-165-A, P.2, and pulling 
the lens out. Next, using a proper screw-driver, take out the 
two small screws which hold the aperture plate in place. 
They are not seen until the film track shoes have been re¬ 
moved. In replacing aperture, or putting a new one in place, 
be sure and set the screws up tight, else the plate may be 
held loosely and scratch the film. 

INSTRUCTION NO. 40.—INTERMITTENT MOVEMENT. 

—In Fig. 262 the intermittent is shown with a part of the 









MANAGERS AND PROJECTIONISTS 


685 


oil casing cut away, so that we can see the interior mechanism. 
The right hand side is the flywheel side. The cam, it will be 
observed, is the lower member, and is driven from the fly¬ 
wheel shaft by a gearing. What looks, like a collar next the 
flywheel hub is not a collar but a part of the casting, as you 
may see by looking at your own mechanism. This illustration 
will be valuable to you when you are following the process 
of disassembling described in Instructions Nos. 8 and 9. 

LUBRICATION.— This is of utmost importance as applies 
to the intermittent oil well. See General Instruction No. 1 
Use none but perfectly clean oil of good grade. Under no 
circumstances use a light oil, such as Three-in-One. Looking 
at your mechanism, and Fig. 262, note that the oil tube nearest 
lamphouse carries oil to the oil well, where it ends directly 



Figure 263 


over the star and bushing. The other tube carries oil to the 
flywheel shaft bearing. 

The oil casing should be filled about one-third full of oil. 
The manufacturer advises against using an oil can to put 
oil into the oil well, because of the likelihood of dirt getting 
into the casing. It recommends the use of a glass syringe, 
which may be had at any drug store. The glass barrel enables 
you to examine the oil before it is put in, and determine 
whether or not it is entirely free from dirt. Keep the syringe 
in a box, protected from dust, and wipe the tip clean before 
using. Small particles of dirt or dust may work serious dam¬ 
age to the closely fitted, highly polished parts, 


686 


HANDBOOK OF PROJECTION FOR 


In Replacing old intermittent parts after disassembly, or in 
installing new parts, be sure they are perfectly clean. If they 
seem to fit too tightly, have patience. These parts are sup¬ 
posed to and must fit snugly. Never Force a tight fitting in¬ 
termittent movement part into place. If you do you probably 
will ruin the-whole thing. If necessary, grind it down, using 
tripoli or rotten stone mixed with oil for the purpose. Never 
Use Emory. After grinding, wash the parts thoroughly with 



Plate 7, Figure 264. 


D-II4-X 


X-II 


X-8 

S2I8L 

S-47I-X 


K-II7-X 

R-I65-X 

W-I07-G 

P-293X 


kerosene or gasoline, and then lubricate with clean oil before 
inserting. 

In Assembling an Intermittent Movement be sure the fly¬ 
wheel or cam shaft fits its bearing without lost motion. If 
there is lost motion, then send part to service station for 
attention. If shaft is too tight, grind it in with rotten stone, 
as before directed. Clean thoroughly with kerosene or gaso¬ 
line, lubricate and place shaft in position, attaching flywheel 
to shaft and placing collar on end of cam shaft. 















MANAGERS AND PROJECTIONISTS 687 

If gears do not run smoothly, then try meshing different 
teeth. If they cannot be made to run smoothly, then turn 
flywheel until cam pin is at upper point of its travel, directly 
under end of oil spout, and using a needle or other sharp in¬ 
strument, make a mark on the flywheel gear by drawing 
the needle around the upper circumference of the cam. This 
is to aid in reassembling the gears after they are disassembled 


Plate 9, Figure 265. 



F-II9-X 


G-I4I-X 

S-437G 


S-438M 

X-3 


X-7 

DII8-X 


C-2II-X 

S-437-G 

S-438M 

K-II7-X 

R-I66X 


S -218 L 


S-I73-X 

GI4I-X 

S-437G 

S-524-X 

C-204-X 

R-I68X 


S-470-X 

S-463-X 


X-ll 

S-575X 


Next apply to the gear teeth a small quantity of a paste 
composed of Arkansas powder mixed with oil, and holding , 
intermittent casing with gears down so that the grinding paste 
will not enter bearings, rotate the flywheel backward and 
forward until the gears are ground in and run smoothly, 
whereupon take out the parts and cleanse them thoroughly in 
a bath of kerosene or gasoline. Repeat grinding process if 
necessary. In reassembling have shafts and bearings perfectly 
clean and lubricated with good oil. Be sure gears mesh as 



























688 HANDBOOK OF PROJECTION FOR 

they did before, by observing mark you made on face of 
flywheel gear. If gears grind in spots only, then apply grind¬ 
ing powder to tight spots only. 

CAUTION— These gear grinding, shaft-fitting directions are 
not recommended by us, except under conditions where they 
are absolutely necessary. Our advice is to have a spare inter¬ 
mittent movement and send the one requiring repairs to a 
service station or to the factory. We have given them because 


Figure 266. 

there are circumstances where the projectionist may be com¬ 
pelled to attempt a repair which will involve these things. 

The rotten stone (Tripoli) and Arkansas powder may be 
had from the Simplex factory or from a Simplex distributor. 

THE TAKEUP. —The Simplex takeup is illustrated in Fig. 
263. See General Instruction No. 23. The illustration, taken in 
connection with General Instruction No. 23 seems to supply all 
necessary instruction. 

SIMPLEX SPEED CONTROL.— The control by means of 
which projection speed is regulated is positive in its action. 
Its flexibility is such that any speed desired between a min¬ 
imum of, say, 40 and a maximum of 140 feet per minute may 
be had. 


MANAGERS AND PROJECTIONISTS 689 

Examining plates 7,8 and 9, which are respectively side, top 
and sectional views of the device, you may readily under¬ 
stand the operating principle, the idea being to cause mechan¬ 
ism driving discs X-8, P.7, to be grasped and driven by fric¬ 
tion discs X-7 and D-118-X, P-9, and to provide means by 
which the projectionist may, by a conveniently located speed 
adjusting knob, (S-438-M, P.7), either thrust disc X-8 further 
between the driving discs, in which case it will be driven 




Bearing carriage whole assemblage, Disc D-118, revolves 
inside it, and main belt wheel X-ll outside it. 

Interior friction disc X-ll. 

Exterior friction disc and shaft. 

Main belt wheel. 

Locking washer. 


more slowly, or withdraw it further out so that it will be 
driven more rapidly. All this is readly understood from an 
examination of the various plates. 

The belting arrangement is shown in Fig. 270, spring F-119- 
X, plate 7, holding the belt, under tension. When the belt 
stretches and becomes too loose, it may. be tightened by 
























































690 HANDBOOK OF PROJECTION FOR 

loosening the bolts holding motor table and lowering the 
motor. 

OIL. —The two main bearings have oil holes held normally 
by a spring supported steel ball. To oil, press the balls down 
with snout of oil can and inject one or two drops of oil. 
Other bearings have plain, open oil holes. 

CAUTION. —Do not get oil on friction discs. If you do, then 
dip a cloth in gasoline and wash disc X-8 and draw it between 
the faces of the other discs until all oil is removed. Oil 
on discs will cause slippage. Keep them clean. 

CAUTION. —In Fig. 270 you will observe a hole in which is 
the end of a shaft. Under the hole is a wing nut. The shaft 
protrudes from the projector frame casting, in which there 
is a hole to receive it. Be sure the shaft is in place in the 
frame casting, and that it is in the hole in the controller cast¬ 
ing and clamped by the wing nut, else the control will not set 
right or be properly supported. 


YOU 

WANT 

GOOD 

PAY 

DON'T YOU? 

WELL, 

THEN 

GIVE 

GOOD SERVICE - 

—THE 

BEST 

THERE 

IS IN 

YOU . 



MANAGERS AND PROJECTIONISTS 691 


Proctor Projector 

T HE U T E Proctor Automatic Projector is of the fully 
enclosed pedestal type. By this we mean that the en¬ 
tire mechanism, including the motor and motor drive, 
is enclosed in a metal casing, only the doors of which are 
removable. The projector is supported on a pedestal, square 
in form, 10 inches each way, with a base 19 inches square, as 
shown in Plate A, Fig. 268. Plate A, Fig. 268, gives the over¬ 
all dimensions which, when the projector sits in a level posi¬ 
tion, are 58 inches front to back by 74 inches in height. The 
lamphouse is 20 inches front to back, 28 inches from its floor 
to the top of its roof and 10}4 inches wide. The mechanism 
casing is 10^4 inches wide by 9 inches front to back, and 15 
inches high in the clear, inside measurement. 

By means of tilting arrangement, 390, Plate F, the pro¬ 
jector may be set to shoot up at an angle of about 15 degrees, 
or to shoot down at any desired angle not exceeding 35 de¬ 
grees. By loosening base bolts 700, Plate A (four of them), it 
is possible to rotate the projector on lower base 555, Plate A. 
This is to prevent the disturbing of the anchorage of the 
lower part of base 555, Plate A, in case it is at any time nec¬ 
essary to change the location of the picture sideways on the 
screen. 

With the ordinary side rails, 517-516, Plate A, furnished with 
the projector, the center of the condenser may be located 21}4 
inches from the aperture, which is probably all that will ever 
be required. In case, however, greater distance is necessary, 
then side rails of greater length may be ordered from the 
company. 

The magazines are \9]4 inches in diameter, inside measure¬ 
ment, the diameter of the 2,000-foot reel being about 15 
inches. 

In giving the following directions for disassembling the 

MECHANISM, OR THE REMOVAL OF ITS VARIOUS PARTS, WE HAVE NOT 
GIVEN THE DIRECTIONS FOR REASSEMBLING BECAUSE REASSEMBLING 
MERELY MEANS A REVERSAL OF THE PROCESS OF DISASSEMBLING, PLUS 
COMMON SENSE AND GOOD JUDGMENT IN MAKING THE NECESSARY 
ADJUSTMENTS, TIGHTENING UP THE VARIOUS SET SCREWS, DRIVING 
IN THE VARIOUS KEYS, ETC, THE MAN WHO DISASSEMBLES A 


692 


HANDBOOK OF PROJECTION FOR 


MECHANISM, AND WHO CANNOT PROPERLY REASSEMBLE THAT WHICH 
HE HAS TORN DOWN, IS NOT A FIT MAN TO HAVE CHARGE OF A PRO¬ 
JECTOR. By THIS WE DO NOT NECESSARILY MEAN THAT SOME VERY 
COMPETENT PROJECTIONIST MIGHT BE UNABLE TO FOLLOW THROUGH 
ALL THE PROCESSES WE HAVE GIVEN, AND GET THE PARTS BACK IN 
GOOD SHAPE, BUT THAT SORT OF MAN MAY BE DEPENDED UPON NOT TO 
ATTEMPT A JOB UNLESS HE KNOWS HE WILL BE ABLE TO FINISH IT. 

INSTRUCTION NO. 1 .— ATTACHED TO COOLING 
PLATE 260, Plate B, is perforated metal eye shield 567, which 



Plate A, Figure 268. 













































MANAGERS AND PROJECTIONISTS 


693 


is riveted to plate 569. The assemblage of the eye shield and 
plate may be removed by taking out two screws, Nos. 701, 
Plate B. 

INSTRUCTION NO. 2.— TO REMOVE COOLING PLATE 
260, Plate B, first follow instructions No. 1, whereupon the 
cooling plate may be detached by taking out the screw in its 
left-hand side. 

INSTRUCTION NO. 3.— BACK OF COOLING PLATE 260, 
Plate B, is the automatic fire shutter. To remove automatic 
fire shutter, first follow Instructions Nos. 1 and 2, whereupon 
the shutter is released by taking out screw No. 266, Plate B. 

INSTRUCTION NO. 4.— ROD NO. 202, PLATE C, connects 



€32 

296 

634 

263 


3iO 

218 

221 

219 

2H 

213 

256 

260 

266 


567 

701 

569 


227 


275 

386 


568 


261 

257 

273 

251 


101 
104 - 
IOO 

102 
105 


248 

244 

247 

262 


30 } 


28? 

105 

106 
276 


275 


PRESSURE ADJUSTMENT 

238 


UNIT 

109 
189 

PRESSURE ADJUSTMENT 


Plate B, Figure 269. 

















































694 


HANDBOOK OF PROJECTION FOR 


at its right hand end with a short plunger, (Stock No. 270) be¬ 
hind the automatic fire shutter. This plunger may be re¬ 
moved by first following Instructions Nos. 1, 2 and 3. In the 
center of the plunger you will see a steel pin. This is not a 
taper pin; it may be driven straight through and out through 
the slot in the casting, whereupon the plunger may be pulled 
out end-wise. 

INSTRUCTION NO. 5. —BACKSHIELD 271, PLATE B, 
may be removed in its entirety by taking out screw 262, Plate 
B, and a similar one in the lower end of bar 257, Plate B. 

INSTRUCTION NO. 6.— Knob No. 386, Plate B, may be re¬ 
moved from the center of the casting by turning it to the 
left. It merely serves as a handle with which to manipulate 
part 271. 

INSTRUCTION NO. 7.— BARS 257, PLATE B, may be re¬ 
moved by first taking out the flat-head screws at their right 
hand end, next removing metal shield 261, Plate B, by taking 
out the two screws in its face, and then removing the two 
screws thus disclosed. 

INSTRUCTION NO. 8.— THE RIGHT AND LEFT HAND 

DOORS of the projector mechanism casing may be taken off 
merely be removing the four screws in the hinges. 

INSTRUCTION NO. 9.— THE UPPER MAGAZINE, includ¬ 
ing the cover of the mechanism casing, may be removed by 
taking out four screws, Nos. 702, Plate A, and 702, Plate B. 

INSTRUCTION NO. 10.— BOTH THE UPPER AND 
LOWER SPROCKETS have four idler rollers, the stock 
number of which is 276. These rollers are carried on a 
bracket. To remove the bracket carrying the rollers, it is 
only necessary to take out the screw holding the bracket to 
its spindle, and then pull the bracket off endwise. 

CAUTION.— IN REPLACING THESE BRACKETS it is 
absolutely essential that you get the rollers spaced an equal 
distance from the film. In order to do this, we would suggest 
that you put a double thickness of film on the sprocket and 
close the idler bracket down until both rollers rest upon it. 
This will space the rollers an equal and about the correct 
distance from the sprocket, whereupon tighten up the screw 
holding the bracket to its spindle. 

INSTRUCTION NO. 11.— THE DISTANCE WHICH THE 
BRACKETS hold the idler rollers of the upper and lower 
sprocket away from the sprocket (see General Instruction No. 
12), is governed by a screw located in an extension at the ex- 


MANAGERS AND PROJECTIONISTS 


695 


treme lower end of bracket arm 273, Plate B, and a similar 
screw at the extreme top end of the upper bracket arm. Set¬ 
ting this screw further in increases the distance of the rollers 
from the bracket and slacking it off sets the roller closer to 
the sprocket. 

INSTRUCTION NO. 12w— TO REMOVE THE LOWER 
BRACKET ARM 273, Plate B, and its shaft 272, Plate C, first 
follow Instruction No. 10, and then remove mechanism casing 
backplate 206, Plate C, by taking out three screws, two on its 
top and one on its lower edge, after which turn knob 239, Plate 
C, five or six turns to the left. Next, take out pin 201, Plate 
C, which releases the automatic fire shutter governor arm. 
Next, remove pin 192, Plate C, after which continue turning 













































696 


HANDBOOK OF PROJECTION FOR 


knob 239, Plate C, to the left until it releases, whereupon the 
backplate may be pulled away. The bracket arm 273, Plate 
B, and its shaft 272, Plate C, may then be taken out by 
slacking off the adjusting screw at its extreme lower end, 
which governs the distance of the idlers from the sprocket. 

Next, loosen the screw which holds spring 274, Plate C, 
sufficiently to remove tension of the spring. Next, remove 
stripper plate 284, Plate B, by loosening set screw in the cast 
iron hub which holds it, and pulling it out to the right. You 
may now loosen the set screw in the face of bracket arm 273, 
Plate B, and drive the bracket off to the right. Having 
removed the bracket, a Woodruff key will be seen in the slot 
in the end of its shaft; take this out and the shaft can be 
slipped out to the left. 

INSTRUCTION NO. 13.— TO REMOVE THE UPPER 
SPROCKET IDLER BRACKET, first follow Instruction No. 
9, after which loosen the set screw and pull the idler bracket 
off its spindle. Next, loosen the set screw in the bracket arm, 
after which it can be pried off the shaft. If it is desired to re¬ 
move the shaft itself, it is necessary to first follow Instruc¬ 
tions Nos. 12, 26 and 27. 

INSTRUCTION NO. 14.— TO REMOVE AUTOMATIC 
STOP, IDLER, PAWL AND SPRING 251, 254, and 650, Plate 
B, first unhook spring 650 and then loosen set screw in the 
lower holding bracket, and pull part 254 off to the right, which 
will release the whole thing. Parts 244 may be taken off 
merely by removing the cotter pin in the back end of shaft 
248, Plate B, and pulling it out to the left. 

INSTRUCTION NO. 15.— STRIPPER PLATE 284, PLATE 
B, may be removed by loosening the set screw in the cast iron 
hub which holds it, and pulling it out to the right. First, shove 
pawl 247 down out of the way, if necessary. 

INSTRUCTION NO. 16.— TOP SPROCKET 105, PLATE B, 
STRIPPER PLATE 283, Plate B, and its holding bracket 282, 
Plate B, may be removed by loosening the two set screws at 
opposite diameters of the hub of the upper sprocket, and the 
set screw which holds bracket 282, Plate B, and pulling the 
assembly off to right. In order to get this sprocket out of 
the stripper plate, it is necessary to loosen or remove the 
screws which hold it to its supporting bracket 282, Plate B. 

INSTRUCTION NO. 17.— APERTURE PLATE 210, PLATE 
B, together with gate and the parts assembled thereon, may be 
removed by taking out four screws in its face. 


MANAGERS AND PROJECTIONISTS 


69 7 


CAUTION.— IN REPLACING THE APERTURE PLATE it 
is necessary that it be lined properly before the screws are 
tightened, because the screw holes are slotted; in order to do 
this it is necessary to thread in a piece of film and center the 
aperture by making sure that the outer edge of both the film 
tracks are an equal distance from the edge of the film. Left 
aperture guide roller is mounted on a shoulder shaft, the 
shaft being held by a taper-head set screw. The guide roller 
should revolve freely, and when properly adjusted should 
engage left side of film, when film is threaded in mechanism. 
Right guide is mounted on gate, and is self adjusting. 

INSTRUCTION NO. 18.— GATE 227, PLATE B, itself may 
be removed simply by removing the cotter pin at the lower 
end of the hinge, and pulling the pin out. 

INSTRUCTION NO. 19.— TO REMOVE TENSION SHOES 
223, Plate B, and replace them with new ones, first remove ten¬ 
sion adjusting thumb screw 211, and a similar one just 
below the aperture, together with the bar and coil springs ; 
then, with a fine pointed screw driver, take out the studs 
upon which the coil springs ride, which go through into the 
tension shoes. The old shoes may then be replaced with 
new ones, and the process of disassemblage reversed, being 
sure that the amount of tension is properly adjusted. See 
General Instruction No. 9. 

INSTRUCTION NO. 20.— REPLACING INTERMITTENT 
UNIT. The entire intermittent unit, Plate B, may be taken out 
by removing three screws, which hold it to the mechanism 
casing. When these three screws are removed, the whole unit 
may be lifted away and replaced with another unit, while any 
repairs necessary are made on the old one. After the in¬ 
termittent unit is removed, looking at the end of the driving 
shaft from which it was disengaged, you will see a slot in 
its center, at one end of which is a small hole. 

Examining the end of the shaft of the intermittent itself, 
you will see a metal tongue, in the end of which is a pin. 
This tongue fits into a groove in the end of the driving shaft, 
and can only be so fitted when the pin enters the hole at 
the end of the slot. This is to prevent there being any 
disturbance of the relation of the intermittent shutter and 
the intermittent movement, when the latter is removed and 
replaced, or removed and replaced by another movement. 
In other words, it is impossible to put on a new intermittent 
movement, or to replace the old one in any way which will 
disturb the timing of the shutter and intermittent movement. 


698 


HANDBOOK OF PROJECTION FOR 



CAUTION.—In replacing the intermittent, always have 
the framing lever at the extreme top of its travel—up as far 
as it will go. In replacing the intermittent, or putting in a 
new one, always set the tongue in approximately the same 
position as the groove, then place the intermittent in posi¬ 
tion, and rock it gently until the tongue seats in the groove, 
so that the face of the casting and the face of the inter¬ 
mittent unit are snugly together, after which the screws 
may be replaced and tightened up. 

INSTRUCTION NO. 21.— FRAMING CARRIAGE ADJUST¬ 
MENT. Should the framing carriage work too hard, or too 
loose, it may be adjusted as follows: On Plate B you will find 
two arrows marked “Pressure Adjustment,” pointing to hexa¬ 
gon nuts. Examining these, you will notice the stud they are 
on has a screwdriver slot in its end. The nuts themselves are 
lock nuts only. For the adjustment of the framing carriage, 
loosen the lock nut, which has a right-hand thread, and 
with the screwdriver turn the bolt to the right to make the 
framing carriage work harder, and to the left to make it 
work easier. Then tighten the lock nuts. 


Plate D, Figure 271. 




























MANAGERS AND PROJECTIONISTS 


699 



INSTRUCTION NO. 22. — REMOVING LOWER 
SPROCKET.—On the hub of knurled knob 568, on crank¬ 
shaft 101, Plate B, is a set screw. Loosen this set screw 
and pull the knob off. 

CAUTION. —This knob is put on with a Woodruff key. 
Don’t lose it. 

Next, remove the taper pin in auto stop cam 102, Plate B. 
Opposite the small end of this pin on the face of the part, 
you will find a center punch mark. Next, remove part 247, 
Plate B, by taking off the nut and sliding the part off its 
spindle, which releases part 247, Plate C, and its shaft, which 
may then be pulled out to the left. Next remove the mechan¬ 
ism side-plate 119, Plate B, by taking out two screws at its 
top end, the screw which holds part 566, Plate B, one screw 
to the right of the oil hole of shaft 101, Plate B, and two 
screws at the lower end. 

It is not necessary to remove the four small round head 
screws in the center of the plate. Next, remove lower 
stripper plate 284, Plate B, as per instruction No. 10. Next, 
loosen the set screws in the lower sprocket (two of them), 


Plate E, Figure 272. 


567 

401 


556 

399 

392 


405 

404 

407 

391 













700 


HANDBOOK OF PROJECTION FOR 


and slide the sprocket off the shaft to the right. Its shaft 
100, Plate B, and its driving gear 103, Plate C, may then be 
pulled out to the left. 

INSTRUCTION NO. 23.—MAIN LENS CARRYING TUBE 

237. —Plate B may be taken out as follows: Remove the 
screw which holds part 566, Plate B ; also the flathead screw 
just above and a little to the right of it. Then, looking 
through the opening under part 566, you will see, on the 
opposite side, two rather large machine screws in the upper 
left-hand corner. Remove them, and the entire casting, aper¬ 
ture plate, gate, and top Plate may be lifted away. Then, 
first having removed lens adapter 228, Plate B, by unscrewing 
it, and taking out two screws at the top of the lens tube car¬ 
rier, which same are immediately below the shaft carrying 
the top sprocket main idler bracket, the whole lens tube can 
be pulled out to the rear- 

INSTRUCTION NO. 24.— TO REMOVE REVOLVING 
SHUTTER GUARD 289, Plate A, together with the revolving 
shutter, it is better to first take off the dissolving shutter 
and bar (not shown in photographs) which is attached to 
the shutter guard. This may be done by removing the 
screw at its right-hand end and pulling the bar out to the 
right. Next, loosen the big set screw in the hub of the re¬ 
volving shutter, which holds it to the shaft, and pull the 
revolving shutter off. You have then only to remove the 
two screws which hold the guard to the mechanism, which 
releases the guard. 

INSTRUCTION NO. 25.— REMOVING REVOLVING 
SHUTTER. (See Instruction No. 24.) 

INSTRUCTION NO. 26.-GEAR 107, PLATE C, is held by 
a set screw and a Woodruff key. The gear may be removed 
by slacking off the set screw, and then screwing out the oil 
cup on top of part 144, Plate C, and pulling the gear off. 

INSTRUCTION NO. 27.— DOUBLE GEAR 115, PLATE C, 
may be removed by first following instruction No. 26, then 
slacking off on the set screw which will be found about 1 % 
inches above and ^2 inch to the right of the upper right-hand 
screw holding part No. 238, Plate B. Back this screw off 
about two turns, whereupon the stud which holds the gear 
may be pulled out to the left, or may be shoved out by 
placing a bar of wood against its inside end and tapping 
gently. In replacing the stud, drive it in gently if it fits 
snugly, and be sure it is not tight enough to bind the gear, 


MANAGERS AND PROJECTIONISTS 


701 


also that it is in far enough so that there is no end play in 
the gear, after which tighten up the holding screw on front 
of the mechanism casing. 

INSTRUCTION NO. 28.— TO REMOVE MAIN DRIVE 
BRACKET 113, and pinion 112, Plate C, take out four screws, 
Nos. 703, Plate C. The bracket and the top end of part 357, 
Plate" D, may then be lifted away. 

INSTRUCTION NO. 29.— TO REMOVE FLYWHEEL 186, 
PLATE C, first remove pin 201, Plate C, and swing automatic 
governor lever arm 196, Plate C, up out of the way. On the 
flywheel hub is a flange collar, 172, Plate C, back of which 
is a coil spring. Press this spring back and in the hub of 
collar 172 you will see a set screw, the removal of which 
releases both collar and spring. Then in collar 171, Plate C, 
you will find another set screw, which should be removed. 
This will release the collar and the plunger pin in the center 
of the flywheel shaft. The flywheel is held to the shaft by 


name plate can be 

REMOVED FOR MOTOR INSPECTION 



Plate F, Figure 273. 




















702 


HANDBOOK OF PROJECTION FOR 


means of a taper pin through the inside center hub. On 
the face of the flywheel close to the small end of the pin 
you will see a small center punch mark. In the rim of the 
wheel are two holes through which a drift-pin can be in¬ 
serted in order to drive out the pin, or tighten it up. After 
driving out this pin, which will require a long tempered steel 
punch with a flat end, you can pull the flywheel off. 

CAUTION. —In performing these various operations, be 
very careful that you remember just how the various parts 
go back. There is no difficulty or mystery about it, nor are 
there any fine adjustments to be made, or any adjustments 
at all for that matter. It is, however, essential that you get 
the various parts back the way they belong, and properly 
anchored in place. 

INSTRUCTION NO. 30.— TO REMOVE GEAR 111, PLATE 
C, which carries two gear faces, you must first follow in¬ 
structions Nos. 28 and 29. Then loosen the set screw in the 
hub of part 568, Plate B, and pull 568 off, removing the 
Woodruff key which you will find in a slot in the end of the 
shaft. Gear 111, Plate C, may then be pulled out. 

INSTRUCTION NO. 31.— TO REMOVE GEAR 180, PLATE 
C, first follow instructions Nos. 28, 29 and 30. Next, turn 
revolving shutter until you can see a set screw in front plate 
of the mechanism, just below the right-hand lower corner of 
the casting, part No. 238, Plate B, carrying the lens tube. 
This set screw holds the stud upon which gear 180, Plate C, 
runs. Back this- screw off two turns, and you can pull the 
stud out, releasing the gear. If it be a little tight, place 
the end of a drift pin on wooden bar against the end of the 
shaft on the side opposite from the gear and tap lightly. 

INSTRUCTION NO. 32.— TO REMOVE FRAMING CAR¬ 
RIAGE, first follow instructions Nos. 20, 28, 29, 30 and 31 
and remove pin 192, Plate C. Next, take out the three screws 
holding part 189, Plate B, which will release same together 
with the entire framing carriage casting. The framing car¬ 
riage carries two phosphor-bronze bushings in which the fly¬ 
wheel shaft runs. We would not advise the projectionist to 
attempt the replacing of these bushings. Should they be¬ 
come worn, it would be better to order entire framing car¬ 
riage casting from the the factory. Its stock number is 190. 

INSTRUCTION NO. 33.— SHUTTER BRACKET UNIT. 
To remove revolving shutter shaft, first remove the dis¬ 
solving shutter. This may be done by taking out the screw 


MANAGERS AND PROJECTIONISTS 


703 


at its right-hand end, and sliding the shutter out at its left 
Next, loosen the set screw which is the hub of the revolving 
shutter, and pull the shutter off the shaft. Then take out 
the two screws in the face of part 127, Plate C, which re¬ 
leases part 127, and yoke 128, Plate C. Next, in one side of 
part 131, you will see a straight pin, which may be driven 
out in either direction. This releases the stud which you 
will see in the face of part 131. It will probably come out 
with a little coaxing, if not, then make a wire hook and, 
reaching in behind, pull the stud out. Next, drive out the 
taper pin in collar 125, Plate C, the small end of which will 
be marked with a center punch mark. You can then pull the 
shutter shaft, 124, out. 

INSTRUCTION NO. 34.— GEAR 134, PLATE C, AND ITS 
SHAFT, may be removed by first following instruction No. 
33, and then driving out the taper pin in the hub of gear 134, 
Plate C, after which the shaft may be pulled out to the right. 
Back of, and meshing with gear 134, Plate C, is a Bakelite 
gear 136, Plate C, which also meshes with, and takes its 
power from the large gear surface of gear 180, Plate C. It 
is only necessary to follow instruction No. 33, drive out the 
pin in collar 125, Plate C, and pull the shutter shaft ahead 
(towards the screen) as far as it will go. Then, just to the 
right of and below the top right-hand screw holding the 
lens casting, Part No. 238, Plate B, to the front frame, is 
the set screw which holds the back end of the stud upon 
which gear 136 rides. Loosen this set screw and the stud 
may be pulled out. 

INSTRUCTION NO. 35.— TO REMOVE ENTIRE RE¬ 
VOLVING SHUTTER BRACKET, it is necessary to first 
follow Instruction Nos. 25, 26, 27, 28, 29, 30, 31, 32, 33 and 34, 
and then remove the three screws holding the shutter bracket 
to the frame. This releases the entire unit, which may then 
be pulled out. 

INSTRUCTION NO. 36.— SPEED CONTROLLER UNIT. 
The speed controller unit, shown in Plate D, may be re¬ 
moved in its entirety by taking out six screws, all num¬ 
bered 703, four of which show in Plate D, the other two 
being behind rod 587, Plate D, disconnecting coupling 649, 
Plate E, and take out pin No. 390, Plate D. 

NOTE. —The position of part 328 has been reversed, the 
action and connection is precisely the same, but the part sets 
just the opposite from the position shown in the photograph. 


704 


HANDBOOK OF PROJECTION FOR 


Next, take out two screws, 330-397, Plate D, and pull out 
the pin at the bottom end of part 328, Plate D. This re¬ 
leases the whole speed controller unit, which may be lifted 
out of the machine. 

INSTRUCTION NO. 37.— THE DRIVING MOTOR, shown 
in Plate E, may be removed by taking out the four hexagon- 
head nuts, which hold it to the frame. Two of them are 
reached by removing the name plate, Plate A, disconnecting 
coupling 649, Plate E, and the wires. 

INSTRUCTION NO. 38.— BRUSH ADJUSTMENT. If any 

motor is D. C., the brushes on right side may be reached by 
taking off name plate, Plate A. In taking out and replacing 
brushes be very careful that you do not disturb their ad¬ 
justment. If the motor is D. C., and it at any time fails to 
develop power, it would be well to first examine the brushes 
and see that they are making proper electrical contact with 
the commutator. 

INSTRUCTION NO. 39.— ADJUSTING HEIGHT OF 
MOTOR. Looking at the under side of the compartment in 
which the motor is contained, you will see four adjustment 
screws. These are for the purpose of adjusting the height 
of the motor. They will not be called into use unless a 
new motor be installed, in which case if the shaft is too high 
or too low, it is only necessary to adjust the height by 
means of these studs, but 

CAUTION.—In doing this, be very careful that you turn 
each one of them exactly the same amount; otherwise you 
will have your motor sitting on an uneven base. 

INSTRUCTION NO. 40.— ADJUSTING AUTOMATIC 
STOP. In case the automatic safety stop does not open the 
driving motor switch when the film breaks, then its ad¬ 
justment should be examined. First make sure that every¬ 
thing is working freely. Try pulling rod 407, Plate E, 
back and forth to make sure it does not bind, then set 
collar 405 so that the plunger extends far enough out from 
the right-hand end of casting D, Plate E, to engage the lip 
on the arm which throws the switch, but not to exceed 1/16 
of an inch. Adjustment F, Plate E, should be so made that 
pawl 247, Plate B, just clears the lower end of pin 244, Plate 
B. With these adjustments made as directed, the automatic 
stop should work perfectly. Remember there may be some 
side shake to the switch throwing lever, therefore have the 


MANAGERS AND PROJECTIONISTS 


705 


pin engage the lip on the lever by 1/16 of an inch when the 
lever is as far as it will go to the right. 

INSTRUCTION NO. 41.— FRICTION DISC WHEEL 329, 
Plate D, has a face approximately of an inch wide. It is 
composed of leather, clamped between two cast iron discs. 
It should wear for a long time. To replace, first order new 
leather drive pulley washers from the factory. To remove, 
first follow Instruction No. 36, then drive out the taper pin 
in the collar to the left of the bearing carrying gear 359, 



Plate G, Figure 274. 



















706 


HANDBOOK OF PROJECTION FOR 


Plate D, after which the shaft may be pulled out to the right 
sufficiently to release the friction disc wheel. 

NOTE. It is possible, by driving out the pin in the collar 
to the left of the bearing carrying gear wheel 359, Plate D, 
and the taper pin in the hub of gear 359, Plate D, removing 
the screw in the face of key 375 and pulling the key out, to 
slip the shaft out to the right, without removing the unit in 
its entirety from the machine. If the shaft sticks in the hub 
of gear 359, however, we would not advise trying to drive 
it out, unless it can be started by tapping on the left hand 
end of the shaft very gently, using a drift pin or a wooden 
bar for the purpose. 

INSTRUCTION NO. 42.— Should any fault develop in fric¬ 
tion disc 376, Plate D, necessitating its removal, it may be 
done as follows: First follow Instruction No. 36. Next 
remove bevel pinion 353 at the lower end of shaft 360, by 
releasing the set screw in the hub of bevel gear 353 at the 
lower end of shaft 360, and prying the gear off, after which 
remove the Woodruff key, which holds gear, from the slot 
in the shaft. Next, drive out the taper pin from part 338, 
Plate D, remembering that the small end of all taper pins is 
marked with a center punch mark. Next, take off part 357 
by releasing the set screw in its hub, prying the part away, 
and taking care of the Woodruff key which holds the part to 
the shaft. The shaft may then be gently driven or shoved 
downward, which will disclose a short key which normally 
is under the lower end of the hub on friction disc 376. Re¬ 
move this key, after which the shaft can be pulled upward, 
releasing the whole assemblage. 

CAUTION: Before attempting a job of this kind, or in fact 
in any considerable job of disassembling, examine the mech¬ 
anism very, very carefully and be sure you understand 
just how everything goes. In reassembling you will be 
greatly aided by the photographs, but you should not depend 
on them too much, partly for the reason that slight struc¬ 
tural changes may be made from time to time, and for the 
further reason that you should not try to make extensive 
repairs and adjustments until you first thoroughly understand 
the mechanism. 

INSTRUCTION NO. 43.— TAKE-UP TENSION ADJUST¬ 
MENT. The take-up tension adjustment is of the friction 
disc type, Plate D, composed of two steel discs between which 
is clamped a fibre disc. One of these discs is attached directly 


MANAGERS AND PROJECTIONISTS 


707 


to the driving mechanism, and has a constant positive speed 
of rotation. The other side of the disc is pinned to the 
shaft that carries the take-up reel, and is rotated wholly and 
entirely through friction with the fibre disc clamped between 
the two. The amount of pull that will be exerted on the 
take-up depends upon the pressure with which the two discs 
are held together, which is regulated by means of a coil 
spring, the tension of which may be adjusted by turning a 
threaded collar. You can rotate this collar by reaching in 
behind the disc, between the disc and the back wall of the 
compartment. The disc is shown as 365, Plate D. The adjust¬ 
ing collar and spring is behind it. 

The whole take-up assemblage, including the shaft upon 
which the lower reel rides, may be removed by releasing the 
set screw in the collar on the shaft in the lower magazine, 
and pulling both locking key and the collar off the shaft. 
Next, take out the two screws which hold part 339, Plate D, 
(then follow Instruction No. 28 if complete speed controller 
unit is not removed) then release set screw in bevel gear No. 
353 at lower end of shaft 360, prying the gear off and remov¬ 
ing the Woodruff key, after which shaft 360 can be pushed up 
slightly, whereupon the whole thing, including the friction 
disc, bevel gear and the take-up shaft may be pulled out. 

INSTRUCTION NO. 44. —Plate G illustrates the method of 
connecting the wires from the projector switch to the junc¬ 
tion box, and from it to the lamp; also the controlling switch 
of the Hallberg Continuous-Feed Arc Control, and the neces¬ 
sary connections. 

INSTRUCTION NO. 45.— CARE AND LUBRICATION OF 
THE LAMP. See Page No. 371. 

INSTRUCTION NO. 46.— LUBRICATION. In the com¬ 
partment shown by Plate C, (left-hand side of the mechan¬ 
ism) are eight oil tubes, two oil cups on the top of the 
revolving shutter shaft bracket, and an oil hole in the side 
of part 113, Plate C. For directions concerning lubrication 
see General Instruction No. 1. In the compartment illustrated 
in Plate D, oil cup A revolves with the shaft. It should have 
about two drops of oil a day. Ball-bearings on both ends of 
shaft 351, Plate D, should be kept lubricated with automobile 
or motor generator cup grease. 

Cups B B B B, Plate D, (four of them) must be kept filled 
with automobile cup grease, and should be given about half a 
turn every second day, provided it is an all-day house; every 


708 


HANDBOOK OF PROJECTION FOR 


four days, if it is an evening house only. The motor oil 
cups and the other two under-hanging oil cups on the same 
shaft are all wick oilers. They may be re-filled without 
removal, simply by inserting the snout of a small squirt can 
in the hole in their side and pumping oil in. This need not 
be done more than once a week. 

In Arm 362, Plate D, at the right of friction disc 329, Plate 
D, is an oil tube, in the top of which is a small screw. Be 
careful and don’t put more than one drop of oil at a time in 
this tube. If you get too much oil in, look out for trouble 
with your speed controller, because the oil will run down, 
get on the face of your friction disc and cause slippage. The 
only two other points to oil are an oil-hole back of part 
568, Plate B, and in the hub on the bearing at the right-hand 
end of shaft 100, Plate B. 

With regard to the intermittent, the oil level ought to be 
just about at the lower edge of the glass and no higher. 

CAUTION: Don’t fill the oil well. Keep the level down to 
the lower edge of the glass. We would recommend that 
the intermittent unit be taken out (See Instruction No. 20b 
the oil cup opened and the oil completely drained out. We 
would also recommend that a little kerosene be squirted in 
and afterwards it ought to be very well cleaned out, at fixed 
intervals, so as to clean the whole movement and the glass, 
after which fresh oil can be put in up to the proper level. 
The manufacturers recommend the use of a special intermit¬ 
tent lubricant which may be obtained from them. It is a little 
thinner than vaseline; this lubricant is recommended by them 
because it has no tendency to leak out through the bearings. 

INSTRUCTION NO. 47.— By turning knob 397, Plate F, to 
the right or left, the friction disc is released and the projector 
stopped without disturbing the motor, and by pressing the 
lever 382, Plate D, the speed of the projector may be checked 
for short titles, etc., this lever operating against the brake 
which bears on the outer edge of under side of friction disc 
376, Plate D. 


KNOWLEDGE IS POWER. 



MANAGERS AND PROJECTIONISTS 


709 


Motiograph De Luxe Model 

T HE Motiograph, De Luxe Model, has a lamphouse of 
ample dimensions. At the time this work goes to press 
there is a lamphouse and lamp of heavier construction 
in process of making. The present lamphouse (1921) is illus¬ 
trated in Fig. 274 A. The metal is of heavy Russian iron. 
Doors are double walled, with a ^ inch ventilated air space 
between. Top has a vent for attaching to a pipe leading to 
open air or projection room vent flue. Dimensions are, front 
to back 16.5 inches, Fig. 274 A, with a recess under the con¬ 
denser, which allows of bringing the arc very close to con¬ 
denser. In effect it adds 2% inches to length of lamphouse. 
Floor to top of gable is 28 inches. 

The condenser casing is so arranged that the projectionist 
has easy access for replacement or cleaning. The condenser 
lenses are held in metal rings which are calculated to equalize 
expansion and contraction of thin edge and thick center of 
lenses, which to an extent controls breakage. There is means 
provided for altering distance between collector and con¬ 
verging condenser lenses at will. The dowser is an “outside” 
one. Maximum possible distance obtainable between center 
of condenser and aperture 21 inches; minimum distance 13 
inches. Minimum distance crater may be placed from face 
of collector lens when lamp is at ordinary working angle, 
2 % inches. 

The arc lamp wire terminal clamps are shown in Fig. 274 B, 
details of the clamp being clearly shown in the picture. The 
carbon clamps are made of a fine grade of gray iron. They 
have a plunger of steel. The gripping surface is sufficient to 
insure good contact between clamp and carbon. 

USEFUL DATA. —The following tabulation shows neces¬ 
sary distance of center of Motiograph De Luxe model pedestal 
from wall when projector is set at different angles, allowing 
a five inch clearance between upper magazine and wall at all 
angles. In this you will of course understand that as the 
projector is tilted at an angle the upper magazine is moved 
forward toward the wall, therefore the base must be moved 
back correspondingly. These figures will be of use in deter¬ 
mining the position of the wire outlets and front to back 
length of the room when same are being planned. 


710 


HANDBOOK OF PROJECTION FOR 


Angle 

0 ° . 

1 ° . 

2 ° . 

Distance 
in Inches 

. 28 4/16 

.. 29 J4 

. 30 

3° . 

. 3054 

4° . 

__ 3134 

50 . 

. 32 3/16 

6 ° . 

. 33 

7° . 

. 33 9/16 

8 ° . 

. 34 3/16 

9° . 

. 34% 

10 ° . 

. 35 9/16 



Distance 

Angle 

in Inches 

11° . 

. 36 3/16 

12° . 

. 37 1/16 

13° . 

. 37 9/14 

14° . 

. 38 3/16 

15° 

. 38% 

16° . 

. 39 y 2 

17° . 

. 39% 

18° . 

. 4054 

19° . 

. 41% 

20° . 

. 42 1/16 



Figure 274 A 

































MANAGERS AND PROJECTIONISTS 711 

INSTRUCTIONS FOR MOTIOGRAPH DE LUXE 

NOTE.—The instructions may seem complicated, but really 
are simple. If followed intelligently and accurately the pro¬ 
jectionist should experience no difficulty in their application. 
“P.1,” “P.3,” etc., means Plate 1, Plate 3, etc. Reference to 
general instructions means the general instructions which 
apply alike to all projectors. They begin on page 592. 

INSTRUCTION NO. 1.— TO REMOVE THE FILM GATE, 
CS-4.P.2, Raise gate latch CS-33,P.2, and pull lower part of 
gate outward until it stops. Press the two hinge knobs CS-20, 


Figure 274 B 

P.2, towards each other until the hinge pins are released. 
Remove top part of gate from between the hinge joints. 
Unhook film gate stop CS-158,P.5, from gate and disengage 
gate slide link SF-84,P.5, whereupon gate slide CS-97,P.5, may 
be removed by sliding it upward on the film gate to allow 
screw heads CS-116,P.5, to pass through openings in ends 
of the slots on gate slide. 

INSTRUCTION NO. 2.— TO REMOVE AUTOMATIC 
FIRE SHUTTER CS-246,P.5, first remove the two screws 
CS-88, P.5, and then circular plate CS-86,P.5. Rack lever 
CS-72,P.5, may be removed by removing screw CS-79 from 
boss CS-75, P.5, at center of lever. 

TO RAISE AUTOMATIC FIRE SHUTTER BY HAND 











712 


HANDBOOK OF PROJECTION FOR 


press pin CS-77,P.2, to the left. This pin projects from upper 
left hand corner of gate. 

INSTRUCTION NO. 3.—TO REMOVE FILM TENSION 
SHOES CS-105 and CS-107,P.5, from film gate slide CS-97, 
P.5, take out screws (4 of them) CS-109,P.6. The tension 
springs which act on these shoes lie between the shoes and 
the gate slide, with their ends against the gate slide. Screws 
CS-109 pass through slots in the ends of the springs. 


NOTE.—WHERE MUCH FIRST RUN, WAXED FILM 
IS PROJECTED, washers may be had for use under screw 
heads CS-109,P.6, of the two upper tension shoes. These 
washers release the tension of the springs, so that the tension 
shoes are guides only. 

INSTRUCTION NO. 4.— TO REMOVE CRADLE CS-249, 

P.5, which holds film to intermittent sprocket, take out screw 
holding spring (not shown) which governs the cradle. Re- 



or £urf?no/i' 


1-7"— 


fooSr fict/ar/orf 


Plate I, Figure 275. 

° f M °t iogr ^ ph De Luxe Mod el- These dimensions may be 
depended upon, taken in connection with the tabulation under “Useful 
Data, for use in locating wire outlets, etc. 





































































MANAGERS AND PROJECTIONISTS 713 

moval of spring releases cradle, or, as the manufacturer calls 
it “intermittent sprocket film tension.” 

NOTE.—Under the spring is a collar, stock number of 
which is CS-188, and on top of the spring is a washer, No. 
CS-189. It is important that collar and washer be in place. 

INSTRUCTION NO. 5.— TO REMOVE FILM GUIDE 
ROLLERS CS-101 and CS-102,P.5, or film guide roller CS-93, 



Plate 2, Figure 276. 













714 


HANDBOOK OF PROJECTION FOR 


P.5, the first two being at top of film gate slide and the last 
named at bottom of intermittent sprocket cradle, it is only 
necessary to take out the screw shaft which holds them. 

INSTRUCTION NO. 6.— TO REMOVE ENTIRE INTER¬ 
MITTENT MOVEMENT GB-75,P.3, AS A UNIT, including 
oil casing, flywheel and intermittent sprocket, open gate in 
order that intermittent sprocket cradle, or tension shoe, be 
released from sprocket. Next loosen screw CS-127,P.6, a few 
turns. Remove screw SF-21, from back end of crank shaft. 
Push crank shaft out of main gear toward operating side of 
mechanism. Remove main gear, loosen clamp screws SF-10, 
P.6, and slide washers they hold (SF-12) away from flange 
of geneva intermittent box, or oil casing. Grasp flywheel 
with left hand and pull it straight out until the geneva box 
is partly removed from frame, then turn the box about one 
quarter turn to the right and pull it out. 

IN REPLACING GENEVA INTERMITTENT BOX, see 
that the “notch” on the rim of the casting is upward, and that 
it engages with stud SF-II, P. 6, the stud being at top of open¬ 
ing in frame into which intermittent box fits. The box of 
necessity fits closely into the frame opening. Do not force 
it in, but work it gently into place. It will go when you have 
it right. If you try to force it you may do great damage. 

INSTRUCTION NO. 7.—TO OPEN THE GENEVA IN¬ 
TERMITTENT BOX, or oil well, GB-75, P. 3, first follow 
Instruction No. 6 and then remove the four screws GB-17, P. 8. 
The cover is not threaded to the box, but is prevented from 
turning and is held in proper relationship to the box by 
dowel pin GB-5, P. 8. The cover is machined to an oil-tight 
fit, hence must be handled very carefully. If it be struck 
or scratched by anything, then when it is replaced the joint 
will in all human probability not be oil tight. 

CAUTION.—In replacing the oil well cover be very careful 
that both surfaces are perfectly clean, but wipe them with 
a clean soft cloth only from which all lint has been removed. 
Also that pin engages with cover made to receive it. 

INSTRUCTION NO. 8.— TO REMOVE INTERMITTENT 
SPROCKET, SHAFT AND STAR, first follow Instruction 
No. 6 and then loosen screws GB-21, P. 3, which hold stripper 
plate stud GB-19, P. 3, to the cover and turn stripper plate 
GB-18, P. 3, away from sprocket. The intermittent sprocket is 
held to its shaft by two taper pins. Before attempting to 
remove these pins study general Instruction No. 5 carefully, 


MANAGERS AND PROJECTIONISTS 


715 


and either use V block shown in Fig. 225 or its equivalent. 
Removal of the pins will release both sprocket, star and shaft. 

NOTE.—We do not advise the projectionist to attempt any 
job which involves removal and replacement of intermittent 
sprocket. We strongly advise the purchase of a spare inter¬ 
mittent unit, and that when such a repair becomes necessary 



CS-18S 

cs -m 
cs- 

•3F- 82 
CS- 
CS-43 
CS '49 
CS-43 
CS - 55 

cs 

cs 
sc 


Plate 3, Figure 277. 




























716 


HANDBOOK OF PROJECTION FOR 


that the spare be inserted and the unit in need of attention 
be sent to the factory, which is the only place such a job 
can be done right. We give instructions, yes, but only to 
help those who are by circumstances forced to attempt the 
removal and replacement of an intermittent sprocket. 

INSTRUCTION NO. 9.— TO REMOVE THE CAM ELE¬ 
MENT OF INTERMITTENT MOVEMENT, GB-77, P. 8, first 
follow Instructions Nos. 6 and 7. Next remove screw GB-26, 
P. 4, which is screw in end of flywheel shaft, and key washer 
GB-25, P. 4, and pull flywheel and pinions GB-22 and GB-24, 
P. 8, off shaft. You may then pull cam and shaft out through 
oil box. 

CAUTION.—Again we advise against attempting repairs on 
intermittent unit. Do it if you are compelled by circum¬ 
stances to, but the parts must, in the very nature of things, 
fit closely. The measurements are in thousandths, or even 
ten-thousandths of an inch. The projectionist is seldom or 
never equipped to work to such accuracy. Better get a 
spare intermittent unit. Costs something, yes, but is worth it. 

INSTRUCTION NO. 10.— ADJUSTMENT OF INTERMIT¬ 
TENT TO ELIMINATE LOST MOTION IN SPROCKET. 
First turn flywheel in direction it normally runs until inter¬ 
mittent sprocket just stops, then give it about an eighth of 
a turn more. This insures the intermittent being “on the 
lock,” as is necessary for this adjustment. Next loosen screw 
GB-8, P. 6 and 8, which will be found in hub of oil casing 
cover carrying intermittent sprocket shaft and bushing. Re¬ 
lease this screw by only about one turn. Do not remove it. 
Next, using small wrench GB-27 (not shown), or some other 
suitable wrench, turn hexagon nut of bushing (between 
sprocket and hub) in whichever direction accomplishes the 
purpose, at the same time “rocking” intermittent sprocket 
with finger. When the movement is tight enough that you 
can barely feel a movement of the sprocket it is right. 
Tighten up screw GB-8 and the job is done. 

CAUTION.—Test for lost motion in sprocket should be 
made immediately after a picture has been projected, because 
then the parts are expanded by heat of operation to their 
operating size. The adjustment should be made when pro¬ 
jector is cold, at which time if there be just a slight move¬ 
ment of sprocket, when parts are heated by operation they 
will be quite sufficiently tight. Remember that if you get 
them too tight undue friction will be set up, which will 


MANAGERS AND PROJECTIONISTS 


717 


further increase expansion and friction. Too much lost 
motion of the intermittent sprocket is bad—too tight an 
adjustment is still worse. 

INSTRUCTION NO. 11.— TO REMOVE UPPER AND 
LOWER SPROCKETS SF-88, P. 5, it is only necessary to 
loosen screw and turn stripper plate back out of the way. 
Then remove screw from sprocket hub and pull sprocket 
off shaft. 

INSTRUCTION NO. 12.— TO REMOVE UPPER OR 
LOWER SPROCKET IDLERS, remove screw SF-40, P. 2, 
which is in end of spindle upon which roller turns. 


- ... 

Plate . 4. 



Plate 4, Figure 278. 























718 


HANDBOOK OF PROJECTION FOR 


INSTRUCTION NO. 13.— TO REMOVE UPPER OR 
LOWER SPROCKET IDLER BRACKETS, SF-30 and SF-31, 
P. 2, it is only necessary to take out SF-33, P. 4 and 6, which 
are on opposite side of center wall of frame from the 
sprockets. 

INSTRUCTION NO. 14. — ADJUSTING SPROCKET 
IDLERS. See general Instruction No. 12, and study same- 



rs-jn 

rs 7 ]2 z 


Plate 5, Figure 279. 


















































MANAGERS AND PROJECTIONISTS 


719 


To adjust upper or lower sprocket idlers loosen screw SF-33, 
P. 5, slightly and, using screwdriver, turn eccentric SF-86, P. 
5, until proper adjustment according to general Instruction 
No. 12 is obtained, whereupon retighten holding screw. 

INSTRUCTION NO. 15.— TO REMOVE FILM TRACKS, 
SF-58 and SF-59, P. 3, first follow Instruction No. 1 and then 



GB-ia 

GB- to 


SP-Q8 

-14 
102 

CS * 141 
-61 


- 80 
79 


PLATE 6 

GB-a 
GB - 9 
G8‘ 11 


-its 

-109 
CS-109 
0S-1O9 
CS US 


SF-71 
5F-rr 
sr-78 


Plate 6, Figure 280. 


































720 


HANDBOOK OF PROJECTION FOR 


remove the eight screws SF-60, P. 3, in face of tracks. This 
releases tracks. 

INSTRUCTION NO. 16.— TO REMOVE APERTURE 
PLATE. Follow Instruction No. 15. Removal of film tracks 
also releases-aperture plate, which is located by pin CS-140, 
P. 3. 

INSTRUCTION NO. 17.— TO REMOVE PROJECTION 

LENS BARREL, consisting of CS-139, CS-144 and CS-146, 
P. 5, remove two screws, CS-141, P. 6. Remove track support 
SF-57, P. 2, by taking out two screws, SF-61, P. 6, which will 
release all parts of lens tube, including focusing screw. 

INSTRUCTION NO. 18.— TO FOCUS PICTURE ON 
SCREEN us.e focusing screw winged thumb nut CS-135, P. 5, 
which protrudes from right hand side of mechanism casing 
near its front edge. 

INSTRUCTION NO. 19.— PLACING LENS IN BARREL. 

At bottom of front end of lens barrel is a clamp screw, CS-148, 
P. 2, by means of which lens tubes are clamped in lens barrel 
To insert lens tube loosen this screw and back it off. A 
sleeve, collar or adapter will be supplied by manufacturer, 
upon application, to reduce diameter of lens barrel to fit any 
desired diameter lens tube. Get collar to fit, insert collar and 
tube. Strike arc, raise fire shutter and project white light 
(without film) to screen. Move focusing screw CS-135, 
P. 5, until lens tube is in center of its travel. Shove lens tube 
in and out until you get edges of light sharply focused on 
screen, whereupon tighten clamp screw CS-148, P. 5, tight, 
and the job is done. The picture may then be sharpened on 
screen by focusing screw when projection is started. 

INSTRUCTION NO. 20.— TO REMOVE GRIPPING DISC 

UNIT SC-100, shown as SC-5, SC-6, P. 3 and 4, remove screw 
CS-28, P. 3, which engages cam slot in the collar. You may 
then withdraw the unit. 

INSTRUCTION NO. 21.— TO DISASSEMBLE GRIPPING 
DISC UNIT SC-100, shown as SC-5 and SC-6, P. 3 and 4, 
follow Instruction No. 20, then drive out taper pin SC-9, P. 3, 
in hub of disc SC-5, P. 3. This releases both discs and they 
may be pulled from shaft. 

INSTRUCTION NO. 22.— TO RELEASE GRIPPING DISC 
SPRING SC-11, P. 6, follow Instruction No. 20, after which 
drive taper pin from pinion on end of shaft. Pull pinion off, 
which releases spring. 


MANAGERS AND PROJECTIONISTS 


721 


INSTRUCTION NO. 23.— TO REMOVE PINION FROM 
GRIPPING DISC SHAFT SC-1, P. 3, follow Instruction No. 
22 . 

INSTRUCTION NO. 24.— THROW-OUT LEVER SC-13,P. 
6, located just at inner surface of gripping disc, is for the 
purpose of releasing gripping disc pinion from gear CS-124, 
P. 6. The gripping discs should be thus released when oper¬ 
ating mechanism by means of the crank. 

INSTRUCTION NO. 25.— TO REMOVE TOGGLE CAST¬ 
ING, shown, removed from mechanism, as CS-117, P. 5, first 
follow Instruction No. 20, then loosen two screws CS-121, 
P. 5, and two screws CS-129, P. 2, and shove out the bronze 
spindle bushing CS-122, P. 2. 

INSTRUCTION NO. 26.— TO DISASSEMBLE TOGGLE 
UNIT, shown removed from mechanism and posed in lower 
right-hand corner of P. 5, first follow Instruction No. 25, then 
remove screw CS-127, P. 5, which will release pulley CS-12o, 
P. 5, and the two gears. To release shaft from casting remove 
nut CS-120, P. 5. 

INSTRUCTION NO. 27.—THE CRANK, SF-48, P. 9, by 
means of which mechanism is operated by hand, engages with 
dowel pin SF-20, P. 3, by means of a ratchet. It is held in 
place on shaft by screw SF-49, in end of shaft—not shown in 
plates. 

INSTRUCTION NO. 28.— Pilot light PL-15, P. 5, is for the 
purpose of lighting interior of mechanism and for threading 
in frame. It is automatically lighted by opening the right 
hand mechanism casing door. The switch is located in the 
fibre base of the lamp, which is operated by means of a two¬ 
cell dry battery located on rear wall of upper magazine. 
When right hand casing door is closed lamp is automatically 
switched off. 

INSTRUCTION NO. 29.— TO REMOVE THE AUTO¬ 
MATIC FIRE SHUTTER GOVERNOR, SF-69,P.4, follow 
instruction No. 1, which removes film gate. Next remove 
governor lever CS-153,P.5, by removing slotted nut CS-157, 
P.5, located on top of frame casting, behind magazine. Next 
remove the two hexagon nuts, SF-82,P.3, in end of shaft, 
which passes through governor unit, and remove hexagon 
nut SF-83,P.5, whereupon entire governor unit will be released. 

INSTRUCTION NO. 30.— TO DISASSEMBLE AUTO¬ 
MATIC FIRE SHUTTER GOVERNOR—First follow In- 


722 


HANDBOOK OF PROJECTION FOR 


struction No. 29, then remove two screws, which hold casing 
SF-77, lower right corner, P. 6, to governor unit, and take 
casing off. To release governor weights, inside of unit, it is 
only necessary to drive out the hinge pins, in either direction, 
they being non-taper pins. 

INSTRUCTION NO. 31.— TO REMOVE REVOLVING 
SHUTTER SUPPORTING UNIT, shown posed on top of 
mechanism casing, CS-44, P. 6, take out the four screws 
separately numbered CS-43, P. 3, which releases the entire 
unit. 

INSTRUCTION NO. 32.— TO DISASSEMBLE REVOLV¬ 
ING SHUTTER UNIT, shown removed from mechanism and 
posed in two positions, CS-44, in P. 3 and P. 6, first follow In¬ 
struction No. 31. Next loosen screw CS-52, P. 3, in collar of 
universal shutter mount, which will release both the mount 



Plate 7. 
FR 9. f¥R- 10. 


Plate 7, Figure 281. 
















MANAGERS AND PROJECTIONISTS 723 

and the shutter shaft. To release shutter drive shaft, CS-53, 
P. 3, loosen screw in collar CS-53. To release shutter shaft 
and shutter driving shaft bushings loosen the set screw 
which holds each, first, of course, having removed the shafts 
themselves.. To remove pinion CS-49, P. 6, and pinion it 
meshes with, first remove the shafts themselves from their 
bushings, and then drive out the taper pins by means of 



GB-23 
NOTCH — 
08-1.1 


Plate 8, Figure 282. 

which gears are locked to shaft. Disc CS-55, P. 6, may be 
removed by driving out the taper pin which holds it. 

INSTRUCTION NO. 33. —TO REMOVE SHUTTER 
DRIVE SHAFT BEARING SF-2, P. 4 and 6, first follow In¬ 
struction No. 6 and then remove double gear SF-22 and 23, 
by taking out screw SF-26, P. 6. Next remove the two 
screws SF-17, P. 6 (arrow only points to one. Other is % 
inch to left) and the bearing will be released. 

Disc SF-6 and Pinion SF-5 are secured to shaft by 
taper pins. The bronze bearings in which the shaft revolves 
are driven in at either end. They are not intended to be re¬ 
placed. When worn it is necessary that a new bearing com¬ 
plete be ordered and installed. 

INSTRUCTION NO. 34.— TO REMOVE DIAGONAL 

SHAFT SF-62, P. 6, remove the two screws (SF-68) which 





724 


HANDBOOK OF PROJECTION FOR 


hold the bearing at either end of shaft, which releases both 
bearings and shaft. 

INSTRUCTION NO. 35.— ADJUSTING, SETTING OR 
TIMING REVOLVING SHUTTER. First carefully study 
general Instruction No. 22 until you thoroughly understand 
the principles involved. In the Motiograph DeLuxe Model 
a universal mount is used in order to enable the removal and 
replacement of the revolving shutter without readjustment, 
or re-setting. The small hexagon nut on front end of hexa¬ 
gon collar is used to clamp the disc carrying pin CS-64, 
lower right corner, P. 3, in position to secure rough adjust¬ 
ment of shutter, the finer adjustment being secured by turn¬ 
ing knob CS-180, P. 4, at top left-hand corner of mechanism. 
The knurled knob at top of rod CS-181, P. 3, is held to rod 
by a set screw which engages a flat spot on rod, and collar 
CS-183, P. 3, is held to shaft by set screw, which also en¬ 
gages with flat spot on shaft. End-shake, or movement of 
rod is prevented by use of adjusting nut CS-184, P. 3, and 
check nut CS-185, P. 3. 

INSTRUCTION NO. 36.— TO ATTACH REVOLVING 
SHUTTER TO ITS SHAFT, dowel pin CS-64, P. 3, must 
enter hole in collar of shutter, and the shutter be clamped in 
place by screw CS-172, P. 3, in hub of shutter. The revolving 
shutter blade is carried by a sort of cradle, the hub of which 
is CS-171, P. 3. This is an excellent arrangement in that it 
permits of the blade being placed right up against the front 
plate of the mechanism—as close to lens as- it is possible to 
get it—in the case of very short focal length projection lens, 
whereas when a very long E. F. projection lens is used the 
shutter may be reversed and actually made to be some dist¬ 
ance beyond the end of the shutter shaft. Under some con¬ 
ditions this is a very valuable feature, in that it permits of 
a virtual lengthening of the shutter shaft. 

INSTRUCTION NO. 37.— TO RELEASE SHUTTER AD¬ 
JUSTING SHAFT CS-181, P. 3, from shutter supporting unit, 
remove screw from opposite end of stud CS-65, P. 3, and to 
release shaft CS-181, P. 3, from frame of mechanism casing 
loosen screw which locks knob CS-180, P. 4, to shaft, having 
first released shaft from shutter supporting unit. 

INSTRUCTION NO. 38.— TO REMOVE SLIDING 
MECHANISM FRAME, which is the vertical sliding frame 
which carries most of the gearing and other parts, first fol¬ 
low Instruction No. 17, then take off the front plate by re- 


MANAGERS AND PROJECTIONISTS 


725 


moving two screws, one at either front top corner of mech¬ 
anism casing, and two screws from the inside of lower cor¬ 
ners of the front plate (front plate is plate which is next 
screen), which screw into the base; also a large screw in the 
middle front of top plate. This latter screw engages the 
large round rod on the frame slides. Next remove lens bar¬ 
rel bracket by taking out three screws CS-31, P. 6, and two 
screws, not shown, which secure other end of bracket to 
round slide rod CS-13, P. 6 . 

INSTRUCTION NO. 39.— TO REMOVE THE FRAMING 
PARTS, which are located on under side of base of mechan¬ 
ism, remove gear segment FR-10, P. 7, by driving out the 
taper pin which secures gear segment to stud FR-11, P. 7. 
Having done this you may then remove double gear FR-7, 
FR-8, P. 7, by taking out screw FR-9, in center of stud on 
which gear rides. Pinion FR-2, P. 7, is removed by driving 
out taper pin which secures it to framing screw FR-I, P. 7. 
Framing handle FR-13, P. 7, is removed by screwing it out, 
using a plier if necessary, lining its jaws with paper to 
prevent scarring handle. 

INSTRUCTION NO. 40.— BALANCING AND TENSION 
OF MECHANISM FRAME. The mechanism frame is bal¬ 
anced by spring SF-41, P. 6. The tension of this spring is 
adjusted by a slotted screw nut located back of top magazine 
and about two inches from front of mechanism frame. The 
tension of the sliding frame is regulated by two screws, SF- 
103, P. 6 and 7, which clamp the sliding frame to the round 
slide rod, CS-13, P. 7. The rear of the sliding frame is guided 
by the square slide rod, CS-14, P. 3, and 6 and the guides are 
adjusted to the square rods by two screws, SF-106, P. 6, one 
near top and one near bottom. These screws should be only 
tight enough to prevent any vibration or shake of sliding 
frame and the tension (ease of sliding) should be regulated 
by screws SF-103, P. 6, which latter should be set just tight 
enough to prevent the sliding frame from “crawling” when 
the projector is in operation. If too loose the frame will 
crawl. If too tight the framing handle will work too hard. 

INSTRUCTION NO. 41— THE SPEED CONTROL. The 
driving disc is mounted directly on the motor shaft, and is 
held in place by a set screw. The speed of projector mechan¬ 
ism is altered by rocking the motor on the shaft of the 
motor support, SC-20, P. 9. Attached to shaft of motor sup¬ 
port, SC-20, P. 9, is an arm, SC-22, which is held in place by 


72 6 


HANDBOOK OF PROJECTION FOR 


two screws, SC-25, P. 9. On the end of the arm is a roller, 
SC-23, P. 9, held in place by a screw in center of roller bear¬ 
ing. This roller engages with a cam, SC-34, P. 9, attached 
to shaft SC-30, P. 9, by set screw SC-35, P. 9. Handle SC-29, 
P. 9, is the speed control lever, or handle. SC-19, P. 4, is an 
armored electric circuit extending to motor through motor 
support bracket SC-20, P. 9. 

INSTRUCTION NO. 42— LUBRICATION. See general In¬ 
struction No. 1, in addition to which the manufacturer 
advises that they furnish a special heavy oil designed for use 
in the oil well of the intermittent movement, and a special 
grease gun is supplied with each Motiograph installation 
with which to inject the oil. The opening for injecting the 
oil is about three-quarters of an inch to the right of the 
locating notch in the top of the box, or oil well, on the left 
side of the sliding frame. “Geneva Lubricating Grease” is 
supplied in either three-ounce or one-pound cans. 

FOR SLIDING DISC SHUTTER CONNECTION a 



Plate 9, Figure 283. 








MANAGERS AND PROJECTIONISTS 


727 


heavier grease, called “Disc Grease,” should be used. It may 
be had of the projector manufacturer in either three-ounce 
or one-pound cans. 

We recommend that you order these lubricants and use 
them for the purposes named. 

THE SPEED CONTROL DISCS should be given a drop of 
oil occasionally. 

THE INNER END OF SPEED CONTROL SHAFT is 
lubricated by an oil tube located about the center of the 
lower front part of the mechanism casing, on the outside. It 
is of vital importance that you do not overlook this oiling 
place. There is an oil hole in the pinion sleeve back of the 
governor. Do not overlook it. The hole in center of take- 
up pulley screw CS-127, P. 6, is an oil hole. 

NOTE.—The Enterprise Optical Company, manufacturers of 
the Motiograph, issue an instruction book, which will be 
sent you free upon application. 

INSTRUCTION NO. 43— TO ADJUST PROJECTOR FOR 
ANGULAR PROJECTION—Loosen two clamp bolts, P. S. 
252, P. 10, and turn hand screw P. S. 250 to the right or to 



Plate 10, Figure 284. 






728 


HANDBOOK OF PROJECTION FOR 


the left to raise or lower rear end of projector until desired 
angle is had, after which tighten clamp bolts P. S. 252. 

CAUTION.—Never attempt to change the projector angle 
by means of hand screw P. S. 250 until the clamp bolts have 
been loosened. 

PARTS FOR MOTIOGRAPH. —De Luxe Model. 

NOTE.—Order by number and description, but do not omit 
the number. The numbers are the manufacturers stock 
number. 


Plate 

No. 

Description. 

— 

CS-1 

Base. 

— 

CS-2 

Top. 

—— 

CS-3 

Front plate. 

2 

CS-4 

Film gate. 

4 

CS-5 

Left side rear door. 

4 

CS-6 

Left side door. 

— 

CS-7 

Right side door. 

7 

CS-8 

Screw to hold mechan¬ 
ism to lower maga¬ 
zine. 

—— 

CS-9 

Hinge stud for film 
gate. 

— 

CS-10 

Screw for hinge stud. 


CS-11 

Stud to guide lens bar¬ 
rel. 

— 

CS-12 

Nut for stud CS-11. 

6 

CS-13 

Round tie rod. 

3-6-7 

CS-14 

Square tie rod. 

— 

eg-is 

Screw for round and 
square tie rod. 

7 

CS-16 

Nut for square tie rod. 

5 

CS-17 

Door latch pin (short). 

— 

CS-18 

Door latch pin (long). 

5 

CS-19 

Gate Latch pin. 

2 

CS-20 

Gate hinge knob 
(short). 

— 

CS-21 

Door latch knob (long). 

■ 

CS-22 

Door latch spring 
(short). 

5 

CS-23 

Door latch spring (long) 

— 

CS-24 

Door hinge pin. 

■ 11 

CS-25 

Screw in gate for stop 
rod. 


CS-26 

Screw to clamp front 
plate to tie rod, 
7-8x8x32. 


C3-2 7 

Screw to hold front 
plate to top and bot¬ 
tom. 

3 

CS-28 

Screw to retain motor 
drive bushing. 

— 

CS-29 

Cross bracket. 

! " 

CS-30 

Bracket screw for round 
rod. 

6 

CS-31 

Bracket screw for square 
rod. 


CS-32 

Stop in for intermit¬ 
tent tension shoe. 

2 

CS-33 

Latch for film gate. 


CS-34 

Collar for gate latch 
No. 33. 


CS-35 

Screw for gate latch 
No. 33. 


CS-36 

Glass for right side 
door (top). 


CS-37 

Glass for right side 
door (left side). 


Plate 

No. 

Description. 

— 

CS-38 

Glass for right side 
door (right side). 

— 

eg-39 

Glass for left side door. 

— 

CS-40 

Retainer clip for glass. 

— 

CS-41 

Screw for retainer clip. 

3-6 

CS-4 2 

Retainer ring for shut¬ 
ter bracket. 

3 

CS-43 

Screw to hold retainer 
ring. 

6-3 

CS-44 

Shutter bracket. 

3 

CS-45 

Screw to retain shutter 
bracket bushing. 


CS-46 

Bushing for shutrer 
shaft. 

- 1 

CS-47 

Bushing for shutter 
shaft drive. 

3-4 

CS-48 

Shaft for shutter. 

6-3 

CS-4 9 

Pinion on shutter shaft 

■ 

CS-50 

Taper pin for shutter 
pinions. 

' 

CS-51 

Collar on shutter shaft 
Hex. 

3 

CS-52 

Screw in shutter shaft 
collars. • 

3 

CS-5 3 

Shaft for shutter drive. 

' 

CS-54 

Pinion on shutter drive 
shaft. 

3-6 

CS-55 

Disc on shutter drive 
shaft. 

— 

CS-56 

Taper pin in discs. 

3 

CS-57 

Collar on shutter drive 
shaft. 

" 

CS-58 

Dowel screw for front 
plate. 

— 

CS-59 

gcrew for shutter brack¬ 
et friction. 

" 

CS-60 

Plug for shutter bracket 
friction. 

~ 

CS-62 

Flange for shutter shaft 
collar. 

ammm 

CS-63 

Hex. nut for shutter 
shaft collar. 

3 

CS-64 

Pin to locate shutter. 

3-6 

CS-65 

Stud for shutter adjust¬ 
ing rod in bracket. 


CS-66 

Screw to retain shutter 
adj. rod stud. 

7 

CS-67 

Fire trap. 

7 

eg-6 8 

Roller for fire trap. 

— 

CS-69 

Bushing for fire trap 
roller. 

— 

CS-70 

Shaft for fire trap roller 

7 

CS-71 

gcrew to hold fire trap 
to base. 

5 

CS-72 

Rack lever for fire shut¬ 
ter. 

— 

CS-73 

Rack for fire shutter. 


MANAGERS AND PROJECTIONISTS 


7 29 


No. 

Description. 

Plate 

No. 

CS-74 

Rivet for rack and hook 

5 

CS-121 


on door stop. ' 



CS-75 

Bearing for rack lever. 

2-5 

CS-122 

CS-76 

Rivet for rack lever 




bearing. 

5-6 

CS-123 

CS-77 

Stud to operate fire 




shutter. 

5 

CS-124 

CS-7 8 

Washer for bearing 




screw. 

— 

CS-125 

CS-79 

Screw in rack lever 

5-6 

CS-126 


bearing. 

5-6 

CS-127 

CS-80 

Fire shutter plate, gear 




side. 

2 

CS-129 

CS-81 

Pinion on fire shutter. 

— 

CS-130 

CS-82 

Shaft for fire shutter. 

— 

CS-131 

CS-83 

Fire shutter plate, col¬ 




lar side. 

— 

CS-132 

CS-84 

Collar on fire shutter. 



CS-85 

Rivet for fire shutter. 

— 

CS-133 

CS-86 

Metal heat shield in 




side gate. 

— 

CS-134 

CS-87 

Stop stud for fire shut¬ 




ter. 

5 

CS-135 

CS-88 

Screw to hold heat 




shield. 

— 

CS-136 

CS-89 

Stop Stud for fire shut¬ 

— 

CS-137 


ter in door. 



CS-90 

Heat shield asbestos. 

— 

CS-138 

CS-91 

Screw for heat shield. 



CS-92 

Film tension plate. 

5 

CS-139 

CS-93 

Roller on tension plate. 

3 

CS-140 

CS-94 

Shaft for roller. 

6 

CS-141 

CS-95 

Spring for intermittent 




sprocket shoe. 

— 

CS-142 

CS-97 

Gate slide. 

— 

CS-143 

CS-98 

Clip for gate slide. 



CS-99 

Rivet for clip. 

5 

CS-144 

CS-100 

Locating stud in gate 




slide. 

— 

CS-145 

CS-101 

Film guide roll, spring 




end. 

2-5 

CS-146 

CS-102 

Film guide roll, plain 

— 

CS-147 


end. 

2 

CS-148 

CS-103 

Spring for guide roll. 


CS-149 

CS-104 

Shaft for guide roll. 

—— 

CS-105 

Tension shoe (long). 

— 

CS-152 

CS-106 

Spring for tension shoe 




(long). 

5 

CS-153 

CS-107 

Tension shoe (short). 

— 

CS-154 

CS-108 

Spring for tension shoe 




(short). 

5 

CS-155 

CS-109 

Screw for tension shoe. 


CS-156 

CS-110 

Tension shoe for inter¬ 

— 


mittent sprocket, out¬ 
side 

5 

CS-157 

CS-111 

Spacing collar for ten¬ 


CS-158 


sion shoe. 

2-3-5 

CS-112 

Tension shoe for inter¬ 

— 

CS-159 


mittent sprocket, in¬ 
side. 

3 

CS-160 

CS-113 

Spacing rod for tension 


CS-161 


shoe. 

— 

CS-114 

Collar between gate 

— 

CS-162 

slide and tension 

7 

CS-163 


plate. 

2 

CS-164 

CS-115 

Screw to hold tension 

— 

CS-165 


plate to gate slide. 


CS-166 

CS-116 

Screw to hold gate 

3 


slide to gate. 


CS-167 

CS-117 

Toggle casting. 

— 

CS-118 

Toggle gear shaft. 

3-4 

CS-168 

CS-119 

Washer on toggle gear 

3 

CS-169 

CS-120 

shaft. 

Nut on toggle gear 

3 

CS-170 

CS-171 

shaft 

3-4 


Description. 

Screw to clamp toggle 
casting. 

Bushing in toggle cast¬ 
ing. 

Gear on toggle shaft, 
steel. 

Pinion on toggle shaft, 
steel. 

Key pin in pinion. 

Take-up pulley. 

Screw in toggle gear 
shaft. 

Screw in tension plug. 

Lens focusing bracket. 

Dowel pin for focusing 
bracket. 

Shaft for focusing 
bracket. 

Pinion in focusing 
bracket. 

Pin to hold pinion No. 
133 to shaft. 

Thumb knob for focus¬ 
ing bracket. 

Wing for knob No. 135. 

Screw to hold focusing 
knob to shaft. 

Screw to hold focusing 
bracket. 

Lens barrel, rear. 

Stud for aperture plate. 

Screw to hold lens bar¬ 
rel to bracket. 

Glass in lens barrel. 

Retainer ring for lens 
barrel glass. 

Tube between lens bar¬ 
rels. 

Screw to hold tube to 
barrel. 

Lens barrel front. 

Bushing in lens barrel. 

Screw to clamp lens 
barrel. 

Lens adapter. 

Lens focusing screw 
rod. 

Governor lever. 

Bushing for lever No. 
CS-153. 

Rod for lever No. CS- 
153. 

Screw shaft for lever 
No. CS-153. 

Nut to hold lever to 
top. 

Stop rod for film gate. 

Hook in end of stop 
rod. 

Friction stud for stop 
rod. 

Ball in friction stud. 

Spring in friction stud. 

Screw in friction stud. 

Cover for crank opening. 

Dowel pin for cover No. 
CS-164. 

Screw for cover No. CS- 
164. 

Shutter, 3 blade. 

Shutter, 2 blade. 

Shutter hub. 

Screw to hold shutter 
to hub. 

Collar for shutter hub. 


730 HANDBOOK OF PROJECTION FOR 


Plate 

No. 

Description. 

3 

CS-172 

Set screw for shutter 
collar. 

— 

CS-173 

Screw to locate shutter 
hub. 

— 

CS-174 

Light shield. 

— 

CS-175 

Glass retainer strip for 
shield. 

— 

CS-176 

Rivet for glass retainer. 

— 

CS-177 

Clip to hold shield tu 
gate. 

*— 

CS-178 

Screw to hold shield to 
gate. 

— 

CS-173 

Ruby glass for shield. 

4-6 

CS-180 

Thumb knob for set shut¬ 
ter. 

3-6 

CS-181 

Screw rod to set shut¬ 
ter. 

3 

CS-182 

Screw to hold knob to 
screw rod. 

3-6 

CS-183 

Collar for shutter set- 
ing screw rod. 

3-6 

CS-184 

Thrust sleeve. 

3-6 

CS-185 

Lock nut for thrust 
sleeve. 

— 

CS-186 

Oil tube for drive shaft. 

— 

CS-187 

Screw to hold oil tube. 

— 

CS-188 

Collar for Int. spkt. 
shoe spring. 

—— 

CS-189 

Washer for int. spkt. 
shoe spring. 

— 

CS-190 

Screw to hold front to 
base vrt. 

5 

CS-246 

Fire shutter, complete. 

2 

CS-247 

Fire trap, complete. 

2 

CS-248 

Light shield, complete. 

5-6 

CS-249 

Inter, sprocket shoe, 
complete. 


CS-250 

2 wing shutter, com¬ 
plete. 

— 

CS-251 

3 wing shutter, com¬ 
plete. 

— 

SF-1 

Sliding frame. 

4-6 

SF-2 

Bearing shutter drive 
shaft. 

— 

CO 

1 

fL. 

Bushing for shutter 
drive shaft. 

6 

SF-4 

Shutter drive shaft. 

6 

SF-5 

Pinion on shutter drive 
shaft. 

6 

SF-6 

Disc on shutter drive 
shaft. 

— 

SF-7 

Taper pin for pinion and 
disc. 

— 

SF-8 

Bushing for upper and 
lower sprocket shaft. 

— 

SF-9 

Bushing for crank shaft. 

6 

PF-IO 

Screw to clamp geneva 
box. 

6 

SF-11 

Stud to locate geneva 
box. 

6 

SF-12 

Clamp for geneva box. 


SF-13 

Clamp pin for geneva 
box. 

— 

SF-14 

Screw for balance spring. 

— 

SF-15 

Key pin for gears. 

6 

SF-17 

Screw for shutter drive 
bearing. 

6 

SF-18 

Main gear, steel. 

— 

SF-19 

Crank shaft. 

3 

PF-20 

Pin in crank shaft. 

3-6 

SF-21 

Thumb screw in crank 
shaft. 

6 

SF-2 2 

Double gear, steel. 

6 

SF-23 

Pinion on double gear, 
steel. 


late 

No. 

Description. 

— 

SF-2 4 

Pinion to drive angle 
shaft. 

— 

SF-2 5 

Double gear shaft. 

6 

SF-2 6 

Screw tu retain double 
gear on shaft. 

2 

SF-2 7 

Screw to retain shaft 
25 in frame. 

3 

SF-2 8 

Aperture plate. 

2 

SF-30 

Roller bracket, upper. 

2 

SF-31 

Rol ler bracket, lower. 


SF-32 

Shaft for roller brack¬ 
ets. 

4-5-6 

SF-33 

Screw in roller bracket 
shaft. 

— 

SF-34 

Taper pin to hold 
bracket to shaft. 

— 

SF-35 

Screw to clamp roller 
shaft. 

■■ 

SF-36 

Stud for roller bracket 
spring. 

2-5 

SF-37 

Spring for roller brack¬ 
ets. 

— 

SF-38 

Film roller shaft. 

2-5 

SF-39 

Film roller. 

2 

9F-40 

Thumb screw for roller 
shaft. 

6 

SF-41 

Balance spring. 

■ 

SF-4 2 

Screw bushing in end 
of spring. 

' 

SF-43 

Screw for adjusting 
spring. 

5 

SF-4 4 

Stripper plate. 

— 

SF-4 5 

Shaft for stripper plate. 

— 

SF-4 6 

Screw for stripper plate. 


SF-4 7 

Screw for stripper plate 
shaft. 

9 

SF-4 8 

Crank. 

5 

SF-4 9 

Retaining screw for 
crank. 

— 

SF-50 

Stud for crank handle. 

— 

SF-51 

Handle for crank. 

’ 

SF-52 

Washer for crank han¬ 
dle. 

— 

SF-5 3 

Screw for crank handle. 

6 

SF-5 4 

Floating disc. 

5 

SF-5 5 

Link for toggle. 

5 

SF-56 

Screw n for toggle link. 

2 

SF-57 

Track "support. 

3 

SF-5 8 

Track, right side. 

3 

SF-59 

Track, left side. 

3 

SF-60 

Strews to tracks. 

6 

SF-61 

Screw to hold track 
support to frame. 

6 

SF-62 

Diagonal shaft. 

— 

SF-6 3 

Pinion governor drive. 


SF-64 

Pinion upper sprocket 
drive. 


SF-65 

Taper pin for diagonal 
shaft pinions. 


SF-6 6 

Bushing for diagonal 
shaft. 

' 

SF-67 

Cap for diagonal shaft 
bushing. 

6 

SF-68 

Screw for cap No. SF- 
67. 

4-6 

SF-69 

Governor support collar. 

3-6 

SF-70 

Pinion on governor. 

6 

SF-71 

Governor weight. 

6 

SF-7 2 

Ball stud for governor 
weight. 

— 

SF-73 

Governor shaft in frame. 

— 

SF-74 

Governor weight collar. 


SF-75 

Pivot pin for governor 
weight. 


MANAGERS AND PROJECTIONISTS 


731 


Plate. 

No. 

Description. 

Plate. 

No. 

Description. 

— 

SF-76 

Spring for governor 


UM-221 

Spring for reel shaft 



weight. 



plunger. 

6 

SF-77 

Governor case. 


TJM-222 

End of reel shaft. 

6 

SF-78 

Screw in governor case. 


UM-223 

Pin in end of reel shaft. 

5-6 

SF-79 

Shaft in governor wght. 


TJM-224 

Thumb nut on reel shaft. 



collar. 


TJM-225 

Screw to retain thumb 

6 

SF-80 

Ball on end of shaft 



nut. 



No. SF-79. 


UM-226 

Brake spring. 

— 

SF-81 

Rivet to hold ball on 


UM-2 27 

Brake pad. 



shaft No. SF-79. 


TIM-22 8 

Brake pad rivets. 

3 

SF-82 

Nuts for collar shaft 


TIM-229 

Brake spring screw. 



No. SF-79. 


TIM-2 30 

Brake spring washer. 

5-6 

SF-83 

Nuts to hold governor 


CM-231 

Door knob. 



shaft in frame. 


CM-232 

Stud for door latch. 

3-5 

SF-81 

Link for gate slide. 


UM-233 

Door latch. 

— 

SF-85 

Nut for gate slide link. 


TIM-234 

Spring for door latch. 

5 

SF-86 

Ecc. stop for roller 


TIM-2 35 

Collar for door latch. 



bracket. 


TIM-236 

Screw for door latch 

— 

SF-S7 

Lock stud for eccentric 



collar. 



stop. 


UM-237 

Door catch. 

5 

SF-88 

Feed and take - up 


TIM-238 

Screw for door catch. 



sprocket. 


TIM-2 39 

Screw for door catch. 

— 

SF-89 

Shaft for feed sprocket. 


TJM-240 

Nut for door catch 

6 

SF-90 

Shaft for take-up 



screw. 



sprocket. 


UM-241 

Fire trap roller. 

— 

SF-91 

Screw for feed and 


UM-242 

Bushing for fire trap 



take-up sprocket. 



roller. 

6 

SF-92 

Feed sprocket pinion. 


CM-243 

Shaft for fire trap 

3-6 

SF-9 3 

Take-up sprocket' pin¬ 



roller. 



ion. 


TIM-24 4 

Screw to hold magazine 

3 

SF-94 

Screw for sprocket pin¬ 



to spider. 



ions. 


CM-24 5 

Felt washers between 

— 

SF-95 

Film footage counter 



magazine and spider. 



bracket. 

4 

UM-27 5 

Upper magazine com¬ 

— 

SF-97 

Screw to hold counter to 



plete, less spider. 



bracket. 




— 

SF-98 

Pinion on counter. 


FRAMER. 

o 

o 

SF-99 

Counter pinion main 

2-7 

FR-1 

Framer screw. 



shaft. 

7 

FR-2 

Pinion on framer screw. 

— 

SF-100 

Screw to hold counter 

— 

FR-3 

Taper pin for framer 



pinion on shaft. 



pinion. 

— 

SF-101 

Screw to hold counter 

— 

FR-4 

Yoke for framer screw. 



bracket to frame. 

— 

FR-5 

Screw for framer yoke. 

6 

SF-102 

Friction screw in frame 

— 

FR-6 

Dowel pins for yoke. 



for square rod. 

7 

FR-7 

Gear for framer. 

6-7 

SF-103 

Friction screw in frame 

7 

FR-8 

Pinion on framer gear 



for round rod. 



No. FR-7. 




7 

FR-9 

Screw shaft for framer 


UPPER 

MAGAZINE. 



gear. 




7 

FR-10 

Framer gear segment. 

— 

TIM-200 

Governor, complete. 

7 

FR -11 

Stud for segment No. 10. 


UM-201 

Spider for upper maga¬ 

— 

FR-12 

Taper pin for segment 



zine. 



No. 10. 

2 

UM-202 

Screew to hold spider to 

3-7 

FR -1 3 

Framer handle. 



machine. 





UM-203 

Magazine bottom. 


TAKE UP. 


UM-204 

Magazine band. 

_ 

TU -1 

Bracket for take - up 


UM-205 

Rivets for magazine 



spindle. 



band. 

— 

TU-2 

Screw to hold bracket 


UM-206 

Magazine door. 



to magazine. 


ITM-207 

Hinge on body. 

— 

TU-3 

Shaft for take-up. 


TIM-208 

Hinge on cover. 

— 

TU - 4 

Collar on take-up shaft. 


UM-209 

Hinge pin. 

— 

TU-5 

Staple on take-up shaft. 


UM-210 

Screw in door hinge. 

— 

TU-6 

Spring in take-up shaft. 


UM-211 

Nut for hinge screws. 

— 

TU-7 

Plunger in take-up 


TIM-212 

Screw for body hinge. 



shaft. 


UM-213 

Wired glass circle. 

— 

TU-8 

End of reel shaft. 


UM-214 

Frame for glass circle. 

— 

TU-9 

Pin to hold end to 


UM-215 

Screw for frame. 



shaft. 


TIM-216 

Nut for frame. 

— 

TU -10 

Ball bearing cone. 


UM-217 

Reel shaft. 

— 

TU-11 

Screw for ball bearing 


UM-218 

Collar on reel shaft. 



cone. 


UM-219 

Staple on reel shaft. 

— 

TU-12 

Housing for ball bearing 


UM-220 

Plunger for reel shaft. 

— 

TU-13 

SJteel ball. 


732 

Plate. 


5 


5 


HANDBOOK OF PROJECTION FOR 


No. 

Description. 

TlJ-14 

Fibre washer. 

TU-15 

Idler pulley arm. 

TU-16 

Idler pulley. 

TU-17 

Screw shaft for idler 
pulley. 

TU-18 

Take-up pulley. 

TU-19 

Nut to hold pulley to 
shaft. 

TU-20 

Idler adjusting screw 
rod. 

TU-21 

Screw to hold adjust¬ 
ing rod to arm. 

TU-22 

Thumb knob for ad¬ 
justing screw rod. 

TU-2 3 

Stem for thumb knob. 

TU-24 

Nut to bold housing to 
bracket. 

TU-25 

Take-up belt. 

TU-26 

Lacing for take-up belt. 

PILOT LAMP. 

PL-1 

Fibre bracket for lamp. 

PL-2 

Contact for lamp switch 
(short). 

PL-3 

Contact for lamp switch 
(long). 

PL-4 

Fibre piece for contact. 

PL-5 

Rivets for fibre piece. 

PL-6 

Screw to hold contact to 
bracket. 

PL-7 

Top plate for lamp 
bracket. 

PL-8 

Bottom plate for lamp 
bracket. 

PL-9 

Screw to hold plate on 
bracket. 

PL-10 

Nut to hold plate on 
bracket. 

TL-ll 

Fibre contact cover. 

PL-12 

Screw to hold contact 
cover. 

PL-13 

Lamp socket. 

PL-14 

Screw to hold lamp 
socket. 

PL-15 

Pilot lamp. 

PL-16 

Lamp cord. 

PL-17 

Bushing between lamp 
bracket. 

PL-18 

Screw to hold lamp 
bracket. 

PL-19 

Battery box. 

PL-20 

Top fibre piece for bat¬ 
tery box. 

TL-21 

Bottom fibre piece for 
battery box. 

PL-2 2 

Rivet for top and bot¬ 
tom fibre. 

PL-2 3 

Cover catch pins. 

PL-24 

Back fibre piece for bat¬ 
tery box. 

PL-25 

Cover for battery box. 

PL-2 6 

Knob for cover. 

PL-27 

Bushing between box 
and magazine. 

PL-2 8 

Screw to hold box to 
magazine. 

PL-29 

Nut to hold box to 
magazine. 

PL-30 

Clamp to hold wire to 
magazine. 

PL-31 

Screw to hold wire to 
magazine. 

PL-100 

Lamp bracket complete. 


GENEVA BOX, OR INTERMITTENT 
MOVEMENT. 


Plate 

No. 

Description. 

8 

GB-1 

Inter, box. 

— 

GB-2 

Bushing for cam shaft. 

8 

GB-3 

Cover for geneva box. 

— 

GB-4 

Stud for geneva box 
cover. 

8 

GB-5 

Dowel pin to locate 
cover on box. 


GB-6 

Threaded bushing to 
clamp eccentric. 

— 

GB-7 

Bushing to clamp ec¬ 
centric. 

5 - 6 - 8 

GB-8 

Screw for eccentric 

clamp bushing. 

6 

GB-9 

Ecc. bushing. 

8 

GB-10 

Geneva star. 

5-6-8 

GB-11 

Intermittent sprocket. 

— 

GB-12 

Taper pin in sprocket. 

— 

GB-13 

Cam shaft. 

— 

GB-14 

Cam. 


GB-15 

Taper pin to hold cam 
on shaft. 

X 

GB-16 

Cam pin. 

8 

GB-17 

Screw to hold cover to 
box. 

6 

GB-18 

Stripper plate. 

6 

GB-19 

Rod for stripper plate. 

— 

GB-20 

Screw to hold stripper 
on rod. 


GB-21 

Screw to clamp stripper 
rod. 

8 

GB-22 

Shutter drive pinion on 
geneva box. 

4-8 

GB-23 

Fly wheel. 

8 

GB-24 

Pinion on fly wheel. 

4 

GB-25 

Key washer for fly 
wheel. 

4 

GB-26 

Screw to hold fly 
wheel. 

' 

GB-2 7 

Wrench for eccentric 
bushing. 

— 

GB-75 

Geneva box, complete. 


GB-76 

Cover for geneva box 
with stud. 

— 

GB-77 

Cam and shaft. 


STEREOPTICON BRACKET. 

4 

SB-1 

Stereo arm. 

— 

SB-2 

Stereo lens ring. 

— 

SB-3 

Stereo lens retainer ring. 

— 

SB-4 

Swivel for lens ring. 


SB-5 

Screw for lens ring 
swivel. 

— 

SB-6 

Screw to clamp swivel. 

— 

SB-7 

Nut to clamp swivel. 

“ 

SB-8 

Screw to clamp lens 
rod. 

’ 

SB-9 

Rod for stereo lens 
ring. 

“ 

SB-10 

Vertical adj. screw for 
lens arms. 

1 

SB-11 

Lock nut for vertical 
adj. screws. 

— 

SB-12 

Support for lens arm. 


SB-13 

Nut for lens arm sup¬ 
port. 

4 

SB-14 

Focusing screw rod. 


SB-15 

Knob for focusing screw 
rod. 

— 

SB-16 

Pin in knob No. 15. 


SB-17 

Screw in end of focusing 
rod. 


SPEED CONTROL. 

3 

SC-1 

Motor drive shaft. 


MANAGERS AND PROJECTIONISTS 


733 


Plate. 

No. 

Description. 

—— 

SC-2 

Pin in motor drive 
shaft. 


SC-3 

Pinion on motor drive 
shaft. 

-- 

SC-4 

Taper pin to hold pinion 
to shaft. 

3 

SC-5 

Outer gripping disc. 

3 

SC-6 

Fibre for gripping disc. 


SC-7 

Plate to hold fibre to 
disc. 


SC-8 

Screw to hold fibre to 
disc. 

3 

SC-9 

Taper pin to hold grip¬ 
ping disc to shaft. 

6 

SC-10 

Inner gripping disc. 

6 

SC-11 

Spring to compress grip¬ 
ping discs. 

6 

SC-12 

Spiral groove bushing. 

6 

SC-13 

Lever pin for grooved 
bushing. 

6 

SIC-14 

Collar on inner disc 
hub. 

3 

SC-15 

Screw in collar No. l'f. 

— 

SC-16 

Motor. 

— 

SC-17 

Conduit elbow. 

— 

SC-18 

Screw for conduit elbow. 

4 

SC-19 

Conduit. 

4-9 

SC-20 

Motor support, for 110 
volt motor. 

— 

SC-21 

Motor support, for 220 
volt motor. 

9 

SC-2 2 

Arm for motor support. 

9 

SC-2 3 

Roller for motor support 
arm. 

9 

SC-24 

Screw for motor support 
arm roller. 

9 

SC-25 

Screw to clamp support 
arm to support. 


Plate. 

No. 

Description. 

1 

SC-26 

Pivot screw for support 
arm. 

— 

SC-27 

Diso on motor. 

— 

SC-28 

Screw for motor disc. 

4-9 

SC-29 

Control lever. 

9 

SC-30 

Control rod. 

— 

SC-31 

Pin to hold control lever 
to rod. 

— 

SC-3 2 

Dial plate. 

— 

SC-33 

Screw for dial plate. 

9 

SC-34 

Cam to control motor. 

9 

SC-35 

Screw to hold cam to 
control rod. 

— 

SC-36 

Conduit clamp. 


SC-37 

Screw to hold conduit to 
mag. wall. 


SC-38 

Nut to hold conduit to 
mag. wall. 


SC-39 

Screw to hold conduit 
to motor support. 

— 

SC-40 

Motor switch. 

— 

SC-41 

Push button for switch. 

— 

SC-42 

Bushing for push but¬ 
ton in mag. 

— 

SC-4 3 

Spacing collar for switch 
(short). 


SC-4 4 

Spacing collar for switch 
(long). 

— 

SC-4 5 

Screw to hold switch to 
mag. 

— 

SC-46 

Nut to hold switch to 
mag. 

9 

SC-47 

Wire cord from main to 
switch. 

— 

SC-4 8 

Conduit from main to 
switch. 

4 

SC-4 9 

Screw to hold motor to 
support. 

— 

SC-100 

Gripping disc unit. 


KNOWLEDGE IS POWER. 



734 


HANDBOOK OF PROJECTION FOR 


The Baird Projector 

T HE Baird projector was the first distinctly heavily built 
type of motion picture projector. Its lamphouse is of 
ample dimensions and its arc lamp is well designed and 
well made. The mechanism is of the “inclosed” type, the 
casing having been removed to show the mechanism in Figs. 
286, 287 and 288. Fig. 285 supplies a general view of the pro¬ 
jector, as well as all necessary dimensional measurements. 
The projector may be tilted to a 25 degree angle. 

INSTRUCTION NO. 1. —To remove revolving shutter, 
310P, P. 2, complete with its housing and lens tube 318P, 
P. 3, proceed as follows: Loosen screw 867P, P. 1, and pull 
the entire shutter, including its casing, straight out away 
from the machine. Shaft 312P, P. 2, which is hexagonal in 
shape, is not attached rigidly to the mechanism, but tele¬ 
scopes into the hexagonal hole in shaft 130P, P. 3. 

INSTRUCTION 2. —In order to remove the casing of the 
projector mechanism, first follow Instruction No. 1, and then 
remove seven screws which secure the front casing to 
mechanism. This releases the entire casing from the 
mechanism, including two doors but not including the gate. 

INSTRUCTION NO. 3. —To remove the cover for the 
shutter casing (not shown in the cut) grasp the cover and 
turn inch to the left. It will then be disengaged and can 
be pulled off. 

INSTRUCTION NO. 4. —In order to remove shutter 310P, 
P. 2, drive; out the taper pin in the hub and pull it off the 
shaft. 

INSTRUCTION NO. 5.—To remove shutter shaft 312P, 
P. 2 and 3, follow Instructions Nos. 3 and 4, which will dis¬ 
close a steel ring containing in its face three machine screws. 
Take out these screws and pull the ring off, which will re¬ 
lease shutter shaft 312P, P. 2 and 3, and its ball bearing. 
Should it become necessary at any time to replace this ball 
bearing, you must order the shaft and bearing complete 
from the manufacturer, as the bearing is placed on the shaft 
under heavy pressure. The stock number of this shaft is 
312P and of the ball bearing 320P. The replacing of this 


MANAGERS AND PROJECTIONISTS 


735 


shaft is merely a reversal of the process of its removal but 
in replacing the steel ring (stock number 319P) be sure the 
ball bearing is properly centered before tightening down 
the three holding screws, else there may be vibration. The 



Tlie Baird Morion Picture Machine 
Vte'.O of operating side:, clo'ed 

/iota,- OOachinc will tilt 17° Dctwcan 
this and z.5° } the, front lags must be sawed. v - 


5 't' 


Figure 285. 








































736 


HANDBOOK OF PROJECTION FOR 


best way to accomplish the centering is to put in the three 
holding screws, tighten them up and then back them off 
about one full turn. Now start the motor, and while the 
projector is running, grasp the steel holding ring between 
your thumb and finger, and you can tell by the sense of 
touch when it is properly centered; whereupon tighten up 
the three holding screws tight. 

INSTRUCTION NO. 6. —The governor, the weight and 
parts of which are shown at 145P, P. 2, is held by two ball 
bearings clamped in the holding casting by screws 853P, P. 2. 



Plate 1, Figure 286. 














MANAGERS AND PROJECTIONISTS 


737 


The entire governor, including the ball bearings, may be re¬ 
moved as a unit by following Instructions Nos. 1 and 2. 
Then remove taper pin 70P, P. 2, and pull off arm 117P, P. 2. 
Next remove screw 141P, P. 2, and a similar s-crew imme¬ 
diately under the arrow head of 853P, P. 2; this releases bar 
MOP, P. 2. Next loosen screws 853P, P. 2, whereupon the 
entire governor including the ball races and beveled gear 
may be pulled out toward the front. 

INSTRUCTION NO. 7. —To remove ball bearing 138P, P. 3, 
and spring 134P, P. 2, follow Instructions Nos- 1, 2 and 6, 
which release the governor as a unit. Now remove screw 
822P, P. 2, and its mate on the opposite side and tap lightly 
on the end of shaft 130P, P. 3. The ball bearing is just a 
tight fit, and by tapping lightly on the end of the shaft with 
a copper or brass punch it will slip off the shaft, and thus 
releases the governor, weight, spring and sleeve. 

INSTRUCTION NO. 8.— To remove spring 134P, P. 2, fol¬ 
low Instruction No. 7. 

INSTRUCTION NO. 9.— To remove weight 145 P, P. 2, 
follow Instruction No.7, and then drive out the pins holding 
the governon-carrying arms. These pins are not tapered and 
may be driven either way. 

INSTRUCTION NO. 10. —To remove ball race on inner 
end of governor shaft, follow Instruction No. 7, and then 
drive out taper pin in hub of gear 136P, P. 2. The large end 
of each taper pin used in this machine may be recognized 
by a file mark on the hub behind the head of the pin. Gear 
and ball race may now be driven off. 

INSTRUCTION NO. 11.— To remove flywheel, 26P, P. 2, 
take out screw in end of shaft and carefully pry off the cap 
under it, whereupon the wheel may be pulled away. This 
also releases pinion 27P, P. 2 and 3. 

INSTRUCTION NO. 12— To remove bearing bracket 30P, 
P. 3, which is also the oil well cover, follow Instruction No. 
11. Then pull off pinion 27P, P. 3, remove screws 867P (six 
of them), P. 2, whereupon the bracket including the cam 
34P, P. 2, gear 33P, P. 2, and its shaft 25P, P. 2, can be pulled 
away as a unit. In removing this bracket pull the parts 
away carefully, moving them straight outward, then up and 
to the right, being careful not to strain any part, else you 
may injure the cam pin or the star or both. 

INSTRUCTION NO. 13.— To remove cam 34P, P. 2, follow 
Instructions No. 11 and 12, and drive out taper pin engaging 


738 


HANDBOOK OF PROJECTION FOR 


the hub of what appears to be gear 33P, P. 2, but is in reality 
the hub of the cam. This will release cam 34P, P. 2, and 
gear 33P, P. 2. Gear 33P, P. 2, is held to cam 34P, P. 2, by 
four screws in the back of the cam; by removing these 
screws the gear is released. 

INSTRUCTION NO. 14.— Shaft 25P, P. 2, runs in a bronze 
bushing pressed into the bracket casting 30P, P. 3. This 
bushing may be driven out and a new one substituted. The 
new bushing may be driven in from either direction, but be 
very careful that you get it started straight, and do not use 
anything but a hard wood punch to drive it. Proceed care¬ 
fully and you will have no trouble. The inner end of the 
bushing should be flush with the casting. 

INSTRUCTION NO. 15. —To remove the intermittent unit, 
which includes shaft 40P, P. 2, star 44P, P. 2, bushing 42P, 
P. 2, eccentric sleeve 43P, P. 2, collar 45P, P. 2, and inter¬ 
mittent sprocket, 41P, P. 2, proceed as follows: Remove 
screw 49P, P. 1, and pull off bracket 48P, P. 1. Release 
screws 833P (two of them), P. 1, and take of intermittent 
stripper 52P, P. 1. Next remove screw 201P, P. 2. Then 
raise up on pin 50P, P. 1, which revolves eccentric sleeve 
43P, P. 1, and disengages the star from the cam. The in¬ 
termittent unit may now be removed by grasping the inter¬ 
mittent sprocket and pulling straight out. 

INSTRUCTION NO. 16. —To remove intermittent sprocket 
41P, P. 2, follow Instruction No. 15 and then drive out the 
two taper pins in the hub of the sprocket. See recommenda¬ 
tion in Instruction No. 57. 

INSTRUCTION NO. 17.— To remove both bushings 42P, 
P. 2, follow Instruction No. 15, drive out taper in the hub of 
star 44P, P. 2. Intermittent shaft may then be removed 
from sleeve 43P, P. 2. There are two bushings in this sleeve, 
and to remove them drive either one clear in against the 
other bushing and drive the old bushings right on through. 
In putting in new bushings use nothing but a hardwood 
punch and be sure to get them started straight. Drive the 
bushings in at either end of the sleeve until they are flush 
with the face of the sleeve. See recommendation in In¬ 
struction No. 57. 

INSTRUCTION NO. 18. —The inner end of shaft 25P, P. 2. 
is carried by a small bronze bushing. To remove this bush¬ 
ing and to replace proceed as follows: First follow Instruc- 
mittent mechanism. The hole which holds the bushing 


MANAGERS AND PROJECTIONISTS 


739 


carrying the end of shaft 25P, P. 2, extends clear through 
to the other side, its open end being plugged up with a loosely 
fitting iron plug. Stick a steel nail or any slim punch 
through the bushing and drive this plug out. Then the 
bushing may be driven out from either end and the new one 
driven in. In driving in the new bushing use nothing but a 
hardwood punch, and be sure to get it started straight. The 
new bushing may be driven in from either end and its face 
must be flush with the casting on the inside end. 

INSTRUCTION NO. 19.— Gear 176P, P. 2, and its shaft, 
gear 163P, P. 2; belt wheel 161P, P. 2; gear 158P, P. 2, and 
the shaft carrying them may be removed as a unit by first 
disconnecting the motor and the take up belts 659P and 
334P, P. 4, and pulling out the hinge pins 338P and 660P, 
P. 4, then removing screws 872P, P. 2, and two others in the 
opposite end of Plate 181P. Next remove screw 152P, P. 1, 
and crank 151P, P. 1, and the taper pin in the shaft behind 
the hub of the crank. Next loosen screw on the inner end 
of shaft 455P, P. 1. This screw is on the gate side just be¬ 
tween sprocket 452P, P. 1, and the casting. Having released 
the screws, turn down the stripper plate which comes up 
between the flanges of the sprocket, and then remove 
sprocket 452P, P. 1, by loosening the screw in the center of 
its hub and pulling the sprocket off its shaft; also pull off 
collar which is on the shaft behind sprocket, after loosening 
two set screws in its hub. This releases the parts. After 
having raised the framing carriage as far as it will go, grasp 
plate 181P, P. 2, and pull the whole thing straight out and 
away. 

CAUTION. —In replacing this part be careful when you 
put the lower sprocket 452P, P. 1, back on the shaft that it 
centers properly between the flanges of the idler roller 
281P, P. 1 (see Instruction No. 55), and that the stripper plate 
is raised up into position between the flanges of the sprocket, 
and its holding set screw well tightened. 

INSTRUCTION NO. 20. —The method of driving the ma¬ 
chine is as follows: When crank driven, gear 158P, P. 2, 
which is attached to take up belt pulley and to the crank 
shaft, drives pinion (stock No. 174) which is secured to the 
lower sprocket shaft 170P, P. 1. This pinion is just inside 
the plate 181P, P. 2, and does not show. It drives the lower 
sprocket shaft and gear 176P, P. 2 and 3 which in turn drives 
the cam shaft pinion 27P, P. 2 and 3. 

When the projector is motor driven, motor pulley 625P, 


740 


HANDBOOK OF PROJECTION FOR 


P. 4, drives friction disc 622P, P. 4, which in turn drives belt 
659P, P. 4. Belt 659P. P. 4, drives pinion 163P, P. 2, being 
attached to pulley 161P, P. 2. Pinion 163P, P. 2, drives 
lower sprocket shaft gear 176P, P. 2 and 3. Gear 176P, P 2 
and 3, then drives the intermittent movement through pinion 
27P, P. 2 and 3. 

INSTRUCTION NO. 21.— To remove gear 176P, P. 2 and 3, 
drive out taper pin in its hub, remembering that the file mark 



800P 


800P 
468P 


472 
209P % 
212R^ 
282R, 
!OOP x 
I03P X 
136 P x 
I44P X 
145 P x 
822P^ 
I34P X 
3I2P^ 
853Pp 
3I0P-J 

l 43 l!l 

853|1 


I63P^i60P 
I64P—40 pj 

|76P-^^gi 

45P ^3BI 

5IP^|§gjg 


470P 


203PS 


140 


867 


68P 


2I3P 


I6IP 


872P 


Plate 2, Figure 287. 







MANAGERS AND PROJECTIONISTS 


741 


on the hub is at the large end of the pin. Gear can then be 
pulled off the shaft. 

INSTRUCTION NO. 22. —To remove lower sprocket shaft 
170P, P. 3, and the inner pinion thereon, follow Instruction 
No. 19 and then drive out taper pin in hub of gear 176P, P. 
2 and 3, whereupon the shaft can be pulled out on the oper¬ 
ating side of the projector. 

INSTRUCTION NO. 23. —To remove bronze bushing carry¬ 
ing lower sprocket shaft 170P, P. 1, follow Instruction Nos. 
19 and 21, whereupon the bushing may be driven out from 
either direction, using a hard wood block and hammer for 
the purpose. In replacing this bushing take note that the 
bushing is longer than the bearing, and be careful that it 
projects or extends the same distance as the old one. 

INSTRUCTION NO. 24. —To remove belt pulley 161P, P. 2 
and gear 163P, P. 2, follow Instruction No. 21 and then 
loosen set screws (two of them), in collar 162P, P. 3, after 
which the pulley and gear can be removed. 

INSTRUCTION NO. 25.— To remove gear 158P, P. 2, and 
the belt pulley attached thereto, follow Instruction No. 19 
and remove collar 163P, P. 3, whereupon the shaft and gears 
can be pulled out. Gear 158P, P. 2 and 3, is attached to the 
crankshaft by means of a taper pin in its hub, and the belt 
pulley next it is also attached in the same manner. 

INSTRUCTION NO. 26. —The crank end of the crankshaft 
is supported by a bronze bushing. To remove this bushing 
and Replace it with a new one follow Instruction No. 19 
whereupon the bushing may be driven out from either direc¬ 
tion and the new one driven in, using only a hard wood 
block for the purpose. 

INSTRUCTION NO. 27. —Just below the intermittent oil 
well in the main frame casting is one of the bushings sup¬ 
porting lower sprocket shaft 170P, P. 1. To remove this 
bushing and replace it with a new one follow instruction No. 
19, whereupon the bushing may be driven out from either 
direction and the new one driven in, using a hardwood block 
for driving. 

INSTRUCTION NO. 28. —The springs which hold the idler 
roller bracket to the sprocket are removed or attached 
merely by slipping them off the studs. 

INSTRUCTION NO. 29. —To remove governor bracket 
137P, P. 2 and 3, carrying governor and the center ball race 
of shaft 100P, P. 2 and 3, follow Instructions Nos. 1 and 2, 


742 


HANDBOOK OF PROJECTION FOR 


then remove taper pin 70P, P. 2, and arm 117P, P. 2, and pull 
out shaft 116P, P. 2. Next remove screw 854P, P. 2, and 
shove upward on gear 103P, P. 2, thus raising both the gear 
and ball bearing above its supporting casting. Now remove 
screws 866P, P. 2 (four of them), whereupon part 137P, P. 2 
and 3, can be pulled away, carrying with it the governor, 
gear 136P, P. 2, and link HOP, P. 2. 

INSTRUCTION NO. 30.—To remove castings IP, P. 1, 
and 2P, P. 3, which support the lens, follow Instruction No. 
1, then take out taper pin 70P, P. 2, pull out shaft 116P, P. 2, 
and remove four screws, one at each corner of the casting, 
first pulling part 2P, P- 3, in by means of knob 10P, P. 1, far 
enough to expose the two screws in lens end of casting. 

INSTRUCTION NO. 31.— To remove knob 10P, P. 1, and 
rod 9P, P. 1, look on the under side of casting immediately 
below rod 9P, P. 1, at the end next knob 10P, P. 1, and you 
will find a small screw. This screw engages a groove in 
shaft 9P, P. 1, and after it has been removed, rod 9P and 
knob 10P may be removed by screwing it out of the arm of 
part 2P, P. 3. In replacing this part do not forget to tighten 
up this retaining screw so that it engages with the groove 
in the shaft, or else the rod will not operate part 2P, P. 3. 

INSTRUCTION NO. 32. —Part 2P, P. 3, is the casting 
which engages or grasps tube 318P, P. 3, which holds the 
lens. The lens tube itself rests inside part 318P, P. 3, so 
that when the parts are assembled and the lens is in place, 
part 318P, P. 3, and the lens tube are tightly clamped to¬ 
gether by screw 867P, P. 1 and 3; and since part 318P, P. 3, 
carries with it shutter blade 310P, P. 2, and shutter shaft 
312P, P. 2 and 3, it follows that by adjusting knob 10P, P. 1, 
the lens and the shutter blade are both moved inward and 
outward when the lens is focused, and thus the shutter is 
maintained at all times at a fixed distance from the lens. 

INSTRUCTION NO. 33.-Top guide roller 19P, P. 1, is 
composed of inner flange 18P, P. 3, outer flange 20P, P. 3, and 
spreading rollers 19P, P. 1, these being held together by 
spindle 14P, P. 3, and spring 16P, P 3. This part may be 
disassembled by removing set screws in the supporting casting 
just back of arrow head 18P, P. 3. The tension of spring 16P, 
P. 3, may be varied at will by loosening the holding set screw 
just back of arrow head 18P, P. 3, and moving shaft 14P, P. 3, 
slightly in or out. 

INSTRUCTION NO. 34. —Aperture plate 5P, P. 1, is held 
in position by four screws. This plate is made of carbon 


MANAGERS AND PROJECTIONISTS 


743 


steel as hard as glass. It may be removed for renewal by 
taking out four screws, one in each corner. 

INSTRUCTION NO. 35.—To remove gate 80P, P. 1, take 
out the four screws holding the main casting to the posts 
and then pull the gate away. The hinges are held by dowel 
pins in addition to the screw. 

INSTRUCTION NO. 36.—Automatic fire shutter flap 91P, 
P. 2, is attached to its shaft merely by being bent around it. 
Its position on the shaft may be adjusted by holding hori¬ 
zontal rack 88P, P. 1, stationary and lifting or lowering, as 



471P 


455P- 

450P- 


45IP 


801 P- 

I8P 

l06Pi 


!OOP 


137P 

I30P 


480P 


48IP 
-31P 
~27P 
-I76P 
-I57P 
'I58P 
"I60P 
"I50P 
|I 62 F» 
>230P 


223P 


16 P 


I4P 


20P 


2P 


i i » 


-. 


Plate 3, Figure 288. 

































744 


HANDBOOK OF PROJECTION FOR 


the case may be, fire flap 91P, P. 2. Fire flap 91P, P. 2, may 
be removed by driving out the spindle from the pinion end. 
In replacing hold the corner of a hardwood block against 
the pinion and drive the shaft into the pinion, after having 
shoved the shaft through the fire flap. The rack engaging 
this pinion may be removed by driving it through the gate 
away from the pinion; use only a hardwood punch for this 
purpose, the door of course being open or off the projector. 
This rack should be kept clean and perfectly free at all times, 
since the shutter drops by gravity alone. 

INSTRUCTION NO. 37— Each of tension shoes 65P, P. 1, 
is pivoted to a plunger which passes through the gate cast¬ 
ing, the shoes being held up against the film by a flat spring, 
the lower end of which is seen at 66P, P. 1. The tension on 
this spring is regulated by nut 68P, P. 2, which is attached 
to a steel screw 67P, P. 1. Thus the projectionist at all 
times is able to give his tension the finest possible adjust¬ 
ment. Spring 66P, P. 1, is so pivoted that it automatically 
equalizes the tension between the two shoes. 

Lower tension shoes 55P, P. 1, are attached to plate 58P, 
P. 1, and are held up by a small flat yoke spring at its rear. 
Plate 58P, P. 1, and lower tension shoes 55P, P. 1, may be 
removed by taking out screw 878P, P. 1, on the upper end of 
the plate. Upper tension shoes 65P, P. 1, may be removed by 
pressing in on the lower end of the shoe until the upper end 
comes out of its engaging slot; turn upper end toward cen¬ 
ter of the gate. It will then be released from its pivot pin. 

INSTRUCTION NO. 38.— Spring 94P, P. 1, is held by two 
screws at its lower end, and serves to hold the film over 
against the steel track at the left of the aperture. It also 
prevents side motion. The main tension spring supplies ten¬ 
sion to the upper shoes. To remove this spring, remove 
screw 72P, P. 2, in the center of nut 68P, P. 2, taking off nut 
68P, P. 2, and pulling out pin 67P, P. 1. In replacing the 
spring be sure that the depression in its face rests on the 
fulcrum properly and that its upper ends engage with the 
plungers of the tension shoes. 

INSTRUCTION NO. 39. —Upper sprocket 452, P. 1, may 
be removed by loosening the screw holding stripper spindle 
454P, P. 1 and 3. Swing the stripper up out of the way, 
loosen the set screw in the hub of the sprocket, and pull 
sprocket off. In replacing sprocket be careful to get it prop¬ 
erly centered between the flanges of its idler rollers. 


MANAGERS AND PROJECTIONISTS 


745 


INSTRUCTION NO. 40.— Upper sprocket shaft 450P, P. 1 
and 3, and gear 451P, P. 2 and 3, may be removed by follow¬ 
ing Instruction No. 39 and then removing collar 453, P. 1, by 
loosening set screws (two of them) in its hub, afterward 
pulling shaft and gear out. 

INSTRUCTION NO. 41. —To remove gear 110P, P. 2, drive 
out the taper pin in its hub and raise the gear off by revolv¬ 
ing it until it disengages from the teeth of 451P, P. 2 and 3. 

INSTRUCTION NO. 42.— To remove shaft 100P, P. 2 and 
3, remove screw in top of mechanism which engages main 
supporting spring 217P, P. 1, then remove nuts 223P, P. 3, and 
take out the two top screws holding mechanism case to the 
top of mechanism, which will allow the whole top of the 
mechanism to be taken off. Next release screw 854P, P. 2, 
and upper and lower screws 868P, P. 2. Now follow Instruc¬ 
tion No. 12, look into the oil well and see the bevel gear on 
lower end of shaft, attached thereto by a taper pin, remem¬ 
bering that the file mark is at the large end of the pin. Drive 
this pin out. Next loosen two set screws in collar resting on 
part 203P, P. 2, and 215P, P. 2, whereupon shaft 100P, P. 2, 
may be lifted out upward. 

INSTRUCTION NO. 43. —The mechanism is held to the 
lower magazine by four screws, the heads of which are seen 
by looking underneath the edge of the casting in the top of 
the lower magazine. Remove these four screws and you may 
lift the whole mechanism away. 

INSTRUCTION NO. 44.— The framing of the carriage is 
accomplished by means of a segment of a gear and pinion at¬ 
tached to the side of the base of the mechanism. Should 
anything at any time go wrong with this mechanism you can 
get at it by removing the machine from the base, whereupon 
its method of disassembling is self-evident- The framing 
mechanism under the base operates a vertical screw 247P, 
P. 4, which engages with a phosphor bronze nut attached to 
the center of the framing carriage. 

INSTRUCTION NO. 45. —The weight of the framing car¬ 
riage is carried by a vertical spring 217P, P. 1, and if there is 
a tendency for the carriage to work down proceed as fol¬ 
lows : Open the motor compartment door, and looking up 
at the bottom of the mechanism you will see a half round 
arrangement with a cap and three screws; this is open at 
one side. Looking in you will see a small nut which has a 
right-hand thread. By tightening this nut slightly the ten- 


746 


HANDBOOK OF PROJECTION FOR 


sion on the framing handle is increased. Later design has a 
plate supported by two lugs in place of the half round sup¬ 
port, the adjustment being the same. 

INSTRUCTION NO. 46.— Where it is desirable to use half¬ 
size lens the company furnishes a special mount with a re¬ 
volving shutter. The half-size lens cannot be used with the 
regular mount as shown at 318P, P. 1 and 3. 

INSTRUCTION NO. 47.— To remove motor drive unit dis¬ 
connect wires leading to switch and remove belt 659P, P. 4, 
by taking out pin 669P, P. 4. Looking under casting 621P, 
P. 4, you will see a horizontal link connected to a vertical 
lever by a screw. Remove this screw. Next take off nut 
securing upper end of toggle link to casting 621P, P. 4. Re¬ 
move screw 658P, P. 4. Motor unit may now be taken out as 
a whole. Motor may be removed from casting 621P, P. 4, by 
removing screws in bottom of casting 621P, P. 4, and screws 
in coupling 650P, P. 4. 

INSTRUCTION NO. 48.— In order to remove driving fric¬ 
tion wheel which bears on friction disc 622P, P. 4, first fol¬ 
low Instruction No. 47, then remove 638P, P. 4, from shaft 
635P, P. 4. This key is held in position by a screw in its 
face. Next remove three screws in the face of the leather 
washer 633P, P. 4, which will release disc wheel. 

INSTRUCTION NO. 49. —To remove the friction material 
on face 625P, P. 4, follow Instructions Nos. 47 and 48 and 
then remove screws in the outer end (you cannot see them in 
the cut) of the friction wheel. This releases the friction 
material, which may be removed and new material be 
secured from the manufacturer and put in its place. The 
friction material will need no turning or trueing up after 
being put in. 

INSTRUCTION NO. 50.— To remove disc wheel 622P, P. 4, 
release the set screw in the belt pulley on the shaft of the 
disc, after first having released the screw in the rim of 
knurled adjusting nut on the rear end of the shaft. Back 
this nut off, whereupon you may pull the friction disc and 
shaft away. 

INSTRUCTION NO. 51. —To adjust the intermittent 
sprocket and cam in order to eliminate lost motion in the 
intermittent, first loosen screw 201P, P. 2, and screw 49P, P. 
1, after which slightly turn eccentric sleeve 43P, P. 1, by 
pressing down on projecting pin 50P, P. 1, at the same time 
revolving the flywheel by hand. When you think you have 


MANAGERS AND PROJECTIONISTS 


747 


it just about right tighten up screw 201P, P. 2, and try the 
intermittent sprocket with your fingers. See General In¬ 
struction No. 5. When you have the adjustment made to 
your satisfaction tighten up screw 49P, P. 1, and the adjust¬ 
ment is completed. 

CAUTION. —Should you, for any reason, remove bracket 
48P, P. 1, be very sure that its face arid the face it fits on are 
perfectly clean when you put them back, because dirt might 
and probably would throw the part out of line and cause 
shaft 40P, P. 1, to bind in bushing 42P, P. 1. Also be very 
sure that screw 201P, P. 2, is set up tight. If it is not it will 
cause trouble. 

INSTRUCTION NO. 52. —End motion in the intermittent 
sprocket (see General Instruction No. 6) may be removed by 
loosening the screw in the steel collar between intermittent 
sprocket 41P, P. 1, and eccentric sleeve 43P, P. 1, and prying 
lightly'' against the rim of the sprocket with a screwdriver, 
letting the point of the screwdriver rest on the collar, which 
will have the effect of forcing the sprocket to the right and 
the collar to the left. Tighten up the screw in the collar 
while it is held in this position. 

INSTRUCTION NO. 53. —In threading the projector, when 
you raise the lower sprocket idler do not jerk it up as though 
you were working with a two-inch bar. Rough handling of 
this idler may get it out of line with the sprocket, which will 
cause the losing of the lower loop. (See General Instruc¬ 
tion No. 12). 

INSTRUCTION NO. 54. —The quantity of oil in oil well 
213P, P. 2, should only be sufficient so you can see the oil 
splash on the oil window when the machine is running. In 
order to clean out oil well 213P, P. 2, remove the screw im¬ 
mediately below the glass window, which will allow the oil to 
drain out, you of course providing something for the oil to 
run into. Replace the screw, flood the well with kerosene 
and give the machine a few turns, after which remove the 
screw, drain out the kerosene and put in fresh oil. (See 
General Instruction No. 1). 

INSTRUCTION NO. 55. —With regard to the idler rollers 
(see General Instruction No. 12), in order to change the 
distance of idler rollers from the sprocket, loosen the clamp¬ 
ing screw in the hub of bracket, one of which is shown at 
800P, P. 1, which will allow of moving the bracket on its 
shaft. In making this adjustment be very careful not to 


748 


HANDBOOK OF PROJECTION FOR 


move the hub of bracket away from the main casting, which 
would cause the idler to be out of line with the intermittent 
sprocket. 

INSTRUCTION NO. 56. —Upper and lower sprockets may 
be turned end for end on their shafts in order to present a 



Plate 4, Figure 289. 










MANAGERS AND PROJECTIONISTS 749 

new tooth surface to the film, if the teeth are worn on one 
side. 

INSTRUCTION NO. 57. —We would by all means advise all 
purchasers of the Baird projector either at the time of pur¬ 
chase or later on to secure a complete part comprised of 40P, 
41P, 51P, 42P and 44P, P. 2. Then when your intermittent 
sprocket, shaft, bushing or star is worn, all you have to do 
is to remove the complete part, substitute the new one and 
send the old one to the factory for inspection and repairs. 
This is in every way much better than to attempt to put on 
a new intermittent sprocket. The intermittent sprocket is 
the heart of a moving picture projector, and it must not only 
be true down to as little as one-tenthousandth of an inch, 
but it must be mounted absolutely true also, and the projec¬ 
tionist is seldom in a position to do a delicate job of this 
kind properly. 

INSTRUCTION NO. 58. —The wear of the bushing carry¬ 
ing shaft 170P, P. 1, supporting lower sprocket 452P, P. 1, 
will have the effect of increasing the distance between the 
sprocket and its idler. Should you begin to have trouble 
with losing the lower loop, first see if you can move the 
outer end of the lower sprocket up and down perceptibly. 
If you can, the bushing is probably somewhat worn and the 
distance between sprocket and idler has increased. The 
remedy is to loosen the idler. (See Instruction No. 55.) 
When you are making this adjustment hold down on the 
sprocket; then adjust idler roller to suit this condition. 

INSTRUCTION NO. 59. —There should be just sufficient 
pressure between friction disc wheel 622P, P. 4, and driving 
friction wheel to cause disc wheel 622P, P. 4, to continue to 
revolve when belt 659P, P. 4, is slipping on pulley. This pres¬ 
sure is regulated by a knurled nut at the rear end of the 
shaft, carrying disc-wheel 622P, P. 4. To test the drive, start 
the motor and grasp the flywheel firmly, causing the belt to 
slip on the pulley. Any unnecessary pressure between fric¬ 
tion disc-wheel 622P, P. 4, and the driving friction wheel will 
cause excessive wear and loss of power and probably heating 
of the motor. 

INSTRUCTION NO. 60.— At the lower end of rod 639P, P. 
4, is a casting supported by a stud attached to the rear wall 
of the compartment. This casting is supported on the stud 
by a clamp lined with fibre. Should at any time the knob 
512P, P. 4, develop a tendency to work up or down while the 


750 


HANDBOOK OF PROJECTION FOR 


motor is running, tighten the screw in this clamp bushing 
sufficiently to hold the rod in place and prevent the knob 
from moving through vibration of parts. 

INSTRUCTION NO. 61. —On the operating side of the pro¬ 
jector at the bottom of the magazine is a horizontal lever, 
the purpose of which is to raise the discwheel end of part 
621P, P. 4, thus releasing belt 659P, P. 4, which operates as 
follows: When ready to start the show raise the lever up 
and start your motor by throwing in the handle of switch 
329P, P. 4, next set speed regulating knob 512P, P. 4, in run¬ 
ning position, if it is not already there. Now when you are 
ready to project the picture drop the lever slowly down with 
one hand and as the fire shutter raises raise the dowser with 
the other hand. 

INSTRUCTION NO. 62.— Belt 334P, P. 4, operates the take- 
up- The take-up gear 342P, P. 4, is on take-up spindle, 348P, 
P. 4, which carries the lower reed. This spindle is supported 
by bar 346P, P. 4, which is hinged to the machine casting on 
the opposite side, just back of the figures 342P, P. 4. The front 
end of this lever, including the take-up spindle, rests in and 
is supported by belt 334P, P. 4. The result is that when the 
reel in the take-up magazine is empty there is very little 
friction on this belt, but as the film is wound on the reel 
the weight increases, and thus an automatically regular take- 
up tension is supplied in excellent form. 

INSTRUCTION NO. 63. —Any angle may be given the pro¬ 
jector as a whole by loosening the clamps which secure the 
legs and raising or lowering the projector to secure the 
desired setting. 

INSTRUCTION NO. 64. —The condenser is supported in a 
metal casing which forms a heat reservoir and will go far 
toward reducing lens breakage. The casing is so designed 
that it may be adjusted to suit various conditions. It is 
advisable that the lens be kept about one-sixteenth of an 
inch apart. 

INSTRUCTION NO. 65. —On the top of the carbon clamp 
of your lamp, under the clamping screw, is a hole which 
should be kept filled with powdered graphite at all times. 
Do this and you will have no trouble with your carbon clamp 
screws working hard. 

INSTRUCTION NO. 66.— The cups on the motor should be 
kept filled with a good grade of medium oil. 


MANAGERS AND PROJECTIONISTS 


751 


NAMES AND NUMBERS OF PARTS FOR BAIRD 

PROJECTOR. 

Order parts by number only. These numbers are the 
manufacturers’ regular stock numbers. The first column in¬ 
dicates the number of the plate or plates upon which the 
part appears. 


Plate. No. Description. 

1 — IP Bracket for lens and aper¬ 

ture plate. 

3 — 2P Slide for V* size lens and 

shutter guard. 

1 — 5P Aperture plate. 

3 — 7 P Spring between lens bracket 

and slide. 

l — 8 P Frame to hold glass on lens 

bracket. 

3 & l— 9P Screw to adjust lens. 

I — 10P Knob of lens adjusting 

screw. 

3 — HP Glass for lens bracket. 

3 — 14P Pin for film guiding roller. 

3 — 16P Spring for film guiding 

roller. 

3 18P Roller for back edge of 

film. 

1 _ 19 P Spreader roller for guiding 

film. 

3 _ 20P Roller for front edge of film. 

2 — 25P Cam shaft. 

— 26P Fly wheel. 

3 & 2 _ 27P Pinion for cam Shaft. 

— 28P Washer for fly wheel. 

— 29P Screw to hold fly wheel 

pinion on cam shaft. 

3 & 2_ 30P Bracket for outside bearing 

on cam shaft—cover for 
oil well. 

3 — 3 IP Bushing for outside bear¬ 

ing on cam shaft. 

3 — 32P Gasket for cam shaft bear¬ 

ing. 

2 33 P Bevel gear on cam shaft. 

2 — 34P Cam. 

1 Sc 2— 4OP Intermittent shaft. 

1 — 4 IP Intermittent sprocket. 

2 & 1 — 42P Bushings for intermittent 

shaft. 

1 — 43P Eccentric sleeve. 

2 — 44P Star wheel. 

2 45 P Collar on intermittent 

shaft. 

1 48P Bracket for outside bear¬ 

ing on intermittent 
shaft. 

1 — 49P Screw for bracket on in¬ 

termittent shaft. 

2 50P Pin to adjust eccentric 

S166V6. 

2 _ 5IP Gasket for eccentric sleeve. 

1 _ 52P Stripper for intermittent 

sprocket. 

1 —. 55P Lower tension shoe. 

— 59P Spring for lower tension 

shoe. 

X __ 65P Upper tension shoe. 

— 66 P Spring for upper tension, 

shoe. 

1 67P Adjusting screw for upper 

tension shoe. 


Plate. No. Description. 

2 —• 68 P Adjusting nut for upper 

tension shoe. 

2 — 72P Screw stop for adjusting 

nut for upper tension 
shoe. 

1 — 80P Gate. 

— 81P Spring for locking pin on 
gate door. 

1 — 84P Plunger for locking gate 

door. 

— 85P Pin for releasing locking 

plunger on gate door. 

1 • 86 P Foot on gate door plunger. 

2 — 87P Knob for releasing pin on 

gate. 

1 — 88 P Rack for fire shutter. 

2 — 89P Pinion for fire shutter. 

2 — 9OP Shaft for fire shutter. 

— 91P Fire shutter. 

1 & 2— 92P Hinges. 

1 —- 94P Spring for edge of film. 

3 & 2—100P Vertical shaft. 

—10IP Bevel gear on lower end of 
vertical shaft. 

2 —103P Bevel gear on center of 

vertical shaft for D. C. 
projector. 

—-104P Ball bearing for center 
bevel gear on vertical 
shaft. 

3 —105P Bevel gear on center of 

vertical shaft for A. C. 
projector. 

3 —106P Nut for center bevel gear 

on vertical shaft. 

2 —107P Driving collar on vertical 

shaft. 

2 —11 OP Gear on top end of ver¬ 

tical shaft. 

2 —-112P Bushing for top end of 

vertical shaft. 

1 —115P Lever engaging fire shutter 

rack. 

2 —116P Shaft carrying levers op¬ 

erating fire shutter. 

2 —117P Lower lever operating fire 

shutter. 

3 —130P Governor shaft. 

—131P Pins for governor balls. 

•—132P Pins for collars on govern¬ 
or shaft. 

2 —-134P Spring for governor for D. 

C. projector. 

—135P Bevel gear on governor 
shaft for A. C. projector. 

2 —136P Bevel gear on governor 

shift for D. C. projector. 

3 —137P Bracket carrying governor 

shaft. 

3 —-138P Ball bearings on governor 

shaft. 


HANDBOOK OF PROJECTION FOR 


752 


Plate. No. 
—139P 

2 —140P 

2 —141P 

—142P 
2 —143P 

2 —144P 

2 —145P 
—146P 

3 —150P 

1, —151P 

1 —152P 
—155P 

3 —157P 

3 & 2—158P 

3 & 2—160P 

2 —161P 

3 —162P 
2 —163P 

2 —164P 

1 —170P 

—174P 

3 & 2—176P 

—181P 
—185P 
—186P 

1 —200P 

2 —201P 

—202P 

2 —203P 

—205P 

—206P 

—207P 

2 & 3—209P 

—210P 
—211P 

2 & 3—212P 

2 —213P 

—214P 

2 —215P 

1 —217P 

—220P 

3 & 2—223P 

—224P 


Description. 

Spring for governor for A. 
C. projector. 

Link connecting governor 
and fire shutter. 

Screws to guide governor 
connecting link. 

Sleeve on governor shaft. 

Fixed collar on governor 
shaft. 

Sliding collar on govern¬ 
or shaft. 

Balls for governor. 

Arm for governor. 

Crank handle shaft. 

Crank arm. 

Screw to hold crank arm. 

Driving pin in crank han¬ 
dle shaft. 

Pulley on crank handle 
shaft. 

Helical gear on crank han¬ 
dle shaft. 

Oil cup on end of crank 
handle shaft. 

Pulley for motor belt on 
crank handle shaft. 

Collar on crank randle 
shaft. 

Pinion on crank shaft for 
motor drive. 

Bushings for pinions on 
crank handle shaft. 

Lower sprocket shaft. 

Pinion on lower sprocket 
shaft. 

Helical gear on lower 
sprocket shaft. 

Bracket for carrying lower 
driving gears. 

Bushing for gear end of 

crank handle shaft. 

Bushing for gear end of ' 

lower sprocket shaft. 

Sliding main frame. 

Screw to lock eccentrio 
sleeve. 

Bushing for inside hearing 
on cam shaft. 

Bushing for lower end of 

vertical shaft. 

Bushing for upper sprocket 
shaft. 

Bushing for crank end of 

crank handle shaft. 

Bushing for sprocket end 
of lower sprocket shaft. 

Hook pins for bracket 

springs. 

Nut for framing. 

Plug for cam shaft bearing 
hole. 

Spring for sprocket 
brackets. 

Glass in front of oil cham¬ 
ber. 

Glass in top of oil cham¬ 
ber. 

Cup for bushing on lower 
end of vertical shaft. 

Spring to support main 
frame. 

Post carrying gate door. 

Nuts for top of posts. 

Nut for bottom of posts. 


Plate. No. 

Description. 

3 

—230P 

Post for front end. 

1 

—236P 

Rollers for upper and low¬ 
er fire valves. 

1 

—237P 

Pins for upper fire valve 
rollers. 


—24 9P 

Pinion on framing screw. 


—251P 

Spring on framing screw. 


—253P 

Gear for framing. 

2 

—254P 

Handle for framing. 


—256P 

Bracket for fire rollers, 
front. 


—257P 

Pins for lower fire valve. 


—258P 

Bracket for fire rollers- 
rear. 


—259P 

Fibre washer for framing 
screw. 

3 & 1—280P 

Bracket carrying roller for 
upper sprocket. 

1 

—281P 

Rollers for upper and lower 
sprockets. 

2 

—282P 

Arm for spring on roller 
bracket shaft 

3 

—283P 

Nut for sprocket roller 
shaft. 

3 

—284P 

Sraft for upper and lower 
sprocket rollers. 


—290P 

Bracket carrying rollers 
for lower sprocket. 

1 

—292P 

Shaft for bracket for lower 
sprocket. 

1 

—300P 

Bracket carrying rollers for 
intermittent sprocket. 

1 

—301P 

Shaft for roller for inter¬ 
mittent sprocket. 

1 

—302P 

Shaft for bracket for in¬ 
termittent sprocket. 

1 

—303P 

Roller for intermittent 

sprocket. 

2 

—310P 

Shutter for D. C. pro¬ 
jector. 


—311P 

Hub for shutter. 

2 & 3—312P 

Shaft for shutter. 


—313P 

Washer clamp for shutter. 

1 & 3—318P 

Tube carrying lens. 

3 

—319P 

Casing for ball bearing. 


—320P 

Ball bearing. 


—321P 

Shutter for A. C. Projector. 

4 

—329P 

Switch for motor. 

4 

—334P 

Belt to drive lower reel. 

3 

—336P 

Door for motor compart¬ 
ment. 

4 

—337P 

Fastener for belt. 

4 

—338P 

Rawhide pin for belt fast¬ 
ener. 

4 

—339P 

Rivet for driving belt. 


—340P 

Stationary bracket carrying 
lamphouse. 

4 

—341P 

Track bars for stationary 
bracket. 

4 

—342P 

Gear on lower reel shaft 
for small reel 1 % core. 

4 

—345P 

Gear and pulley for driving 
lower reel. 


—346P 

Arm carrying lower reel. 

4 

—348P 

Shaft for lower reel. 

4 

—349P 

Pin carrying pulley on 
lower reel arm. 


—350P 

Collar on lower reel shaft. 


—351P 

Latch for lower reel shaft. 


—352P 

Plunger in lower reel shaft. 


—353P 

Spring in lower reel shaft. 


—354P 

Pin for latch in lower reel 
shaft. 


MANAGERS AND PROJECTIONISTS 753 


Plate. No. 

Description. 

Plate. No. 

Description. 

4 

—357P 

Guard for belt on arm 


—628P 

Pulley on shaft of driven 



carrying lower reel. 



friction disc. 

3 

—358P 

Lug for hinge on stand. 


—629P 

Bushing for driven friction 

4 

—360P 

Bracket for motor switch. 



disc shaft. 

1 & 3 

—450P 

Slhaft for upper sprocket. 


—630P 

Bushing for ball bearing 

3 & 2 

:—451P 

Gear on upper sprocket 



end of driven friction 



shaft. 



disc. 

1 

—452P 

Upper sprocket and lower. 


—631P 

Bushing for driving shaft on 


—453P 

Collar on upper sprocket 



motor drive. 



shaft. 


—632P 

Adjusting nut for driven 

3 & 1 

—454P 

Shaft for upper sprocket 



friction disc. 



stripper. 

4 

—633P 

Retaining washer on hub 

3 & 1 

—455P 

Stripper for upper sprocket 



of driving friction wheel. 



and lower. 

4 

—635P 

Shaft for driving friction 

3 

—465P 

Main arm carrying stere- 



wheel. 



opticon. 

4 

—639P 

Friction lever for moving 

2 

—468P 

Coupling between stereop- 



friction wheel. 



ticon arm and lens. 

4 

—650P 

Leather band for flexible 

2 

—469P 

Rack for stereopticon arm. 



coupling. 

2 

—4 70P 

Rod for stereopticon arm. 

4 

—652P 

Rod for speed control. 

2 &3- 

—471P 

Knob for adjusting stere¬ 

4 

—653P 

Ball bearings for friction 



opticon. 



drive. 

2 

— 472P 

Pinion for stereopticon. 

4 

— 659P 

Belt for motor drive. 

O 

O 

— 47 3P 

Pivot pins for stereopticon 

4 

— 660P 

Rawhide pin for driving 



rack. 



belt fastener. 

3 

— 475P 

Yoke end for stereopticon. 

2 -1- 

3— 800P 

Clamp screws. 


— 476P 

Collar on stereopticon 

2 

—822P 

Stock screw. 



rack. 

1 

—827P 

Stock screw. 

3 

—4 80P 

Housing for stereopticon 

1 

— 829P 

Stock screw. 



lens. 


—801P 

Clamping screw. 

3 

— 481P 

Retaining ring for 2%" 

1 

— 833P 

Machine screw, stock. 



stereopticon lens. 

2 

— 853P 

Stock machine screw. 


— 482P 

Stereopticon lens 2%". 

2 

— 854P 

Stock machine screw. 

4 

— 621P 

Frame for friction drive. 

3 & 

2 — 867P 

Stock machine screw. 

4 

— 622P 

Friction driven disc. 

2 

—868 P 

Stock machine screw. 

4 

— 623P 

Hub for driving friction 

2 

— 872P 

Stock machine screw 


• 

wheel. 

1 

— 896P 

Sstock machine screws. 

4 

— 624P 

Arm for moving driving 

1 

— 9 06P 

Stock machine screw. 



friction wheel. 

2 

—866 

Stock machine screw 

4 

— 625P 

Face for driving friction 

2 . 

— 70 

Pin. 



wheel. 

3 

—801 

Nut holding housing 4 80 to 

4 

—626P 

Pivot base for motor frame. 



yoke 475. 


—627P 

Clamp washer for face of 

4 

—122 

Pin for hinge of door 336. 


driving friction wheel. 


KNOWLEDGE IS POWER 







754 


HANDBOOK OF PROJECTION FOR 


The Motiograph, No. 1-A 1916 
Model 

I NSTRUCTION NO. I.— GEAR COVER M-A, IP, P. 2, 
carries the parts shown attached thereto in P. 2- By 
loosening thumb screws 233 (two of them), P. 2, and 
thumb screw 233, P. 4, the gear cover may be pulled away, to¬ 
gether with the parts attached thereto. 

INSTRUCTION NO. 2. —Instruction No. 2 omitted. 
INSTRUCTION NO. 3.— FRONT PLATE 172, P. 4, which 
carries the objective lens, may be removed by loosening thumb 
screws 99A (two of them), P. 4, and raising the outer end of 
spring 275, P. 4, at the top edge of the front plate, at the 
same time pulling to top of the plate outward and up. 

INSTRUCTION NO. 4.— THE MACHINE GATE is opened 
by pressing on knob 125P, P. 1. This knob is the end of the 
gate latch rod, which extends inward and carries gate latch 
screw 220, P. 1, as may be seen by removing the front plate 
(see Instruction No. 3) and looking inside the mechanism. 
Gate latch screw 220, P. 1, is threaded into this knob and 
may be removed by a screwdriver. Looking inside the 
mechanism you will see, in the upper left hand corner, a 
collar on the gate latch rod, held in place by a set screw. 
This collar serves to compress a small spiral spring. In 
order to remove this spring, loosen the set screw in the 
collar and remove screw 220, P. 1, whereupon the gate latch 
rod may be pulled inward, thus releasing both the collar and 
spiral spring. Should the gate latch at any time fail to 
work properly, it is probable that the head of gate latch 
screw 220, P. 1, has become worn, and a new one should be 
ordered and installed. It is also possible that the spring has 
become weak, in which case it should be taken out and either 
stretched until it gives sufficient compression or a new one 
may be installed. 

INSTRUCTION NO. 5.— TO REMOVE THE MACHINE 
GATE, unscrew knob 127, P. 1, lift governor rack-bar, 168, P. 2, 
off standard 83, P. 1, and lift the gate away. In replacing the 
gate don’t forget to hook the end of the rack bar to standard 

83 P. 


MANAGERS AND PROJECTIONISTS 


755 


CAUTION. —It will probably never be necessary to take 
the gate apart, and if it is for any reason necessary to do so, 
we would not advise the projectionist to undertake this par¬ 
ticular thing unless he is compelled to. When the gate is 
once taken apart it is a somewhat difficult matter to re¬ 
assemble it properly, and we would suggest that instead, 
should it ever be necessary to make any repairs to its in¬ 
ternal mechanism, the gate be sent to the factory. The film 
tension bars, 96 A, P. 1, and the tension spring can, of 
course, be removed without taking the gate apart. 

INSTRUCTION NO. 6.— APERTURE PLATE 162A, P. 1, 
may be removed by taking out screws (four of them) 217, P. 1. 
These screws are small, therefore be careful or you will 
lose them. Better lay a piece of paper underneath to catch 
them should they fall, or, better still, handle them with a 



Plate 1, Figure 290. 





























756 


HANDBOOK OF PROJECTION FOR 


magnetized screwdriver. (See General Instruction No. 19.) 

INSTRUCTION NO. 7. — TENSION SPRINGS AND 
SHOES.—Tension shoes, 96A, P. 1, are held in place by a one- 
piece, square, flat spring, 174A, P. 2, which may be seen by 
looking into the gate edgewise. This spring not only holds the 
tension shoes in place, but also supplies them with normal 
tension. The action may be plainly seen by pressing on one 
of the shoes, at the saime time looking into the gate edge¬ 
wise. Spring 259P, P. 2, bears on the lower edge of spring 
174A, P. 2, and by means of thumb screw 245, P. 2, may be 
caused to supply auxiliary or increased tension to the bot¬ 
tom of the tension shoes. Tension shoes, 96A, P. 1, may be re¬ 
moved as follows: Loosen screws 294 and 222, P. 2, and swing 
cooling plate over to the left out of the way. Next block 



Plate 2, Figure 291. 























MANAGERS AND PROJECTIONISTS 


757 


fire shutter, 163, P. 2, up out of the way. You will then see 
spring 174A, which is held by two round-head screws, one 
at either side of the aperture. First, having backed off on 
thumb screw 245, P. 2, until spring 259, P. 2, is out of contact 
with spring 174A, remove the two screws holding spring 
174A, and pressing in on the tension shoes with the thumb 
and finger of one hand and in on the top and bottom of 
spring 174A, P. 2, with the thumb and finger of the other 
hand, slip spring 174A down slightly, which will unhook 
it from the tension shoes and release both them and the 
spring. 

In replacing the shoes and spring, place the shoes in 
proper position so that the hooks on the lugs will point 
downward, and pressing spring 174A down flat, slip it up 
under the hooks until they are engaged, whereupon replace 
the screws and swing the cooling plate back in place, tighten 
up its holding screws and the job is done. 

INSTRUCTION NO. 8.—AUTOMATIC FIRE SHUTTER 
BLADE, 163P, P. 2, may be removed as follows: First follow 
Instruction No. 5; next remove screws 219, P. 1, and another 
similar screw about three inches immediately above. Loosen 
screw, 294, P. 2, and you can lift the entire front plate of the 
gate away, which will release automatic fire shutter, 163P, 
P. 2. 

INSTRUCTION NO. ».—Tension Spring, 259, P. 2, may be 

removed by following Instruction No. 8, and then taking out 
screws, 260P, P. 2. 

INSTRUCTION NO. 10—TENSION.—(See General In¬ 
struction No. 9). The tension may be increased in two ways, 
first by removing spring, 174 A, P. 2 (see Instruction No. 7), 
and bending it in proper direction to supply added tension, or 
by tightening up on thumbscrew, 245 P, P. 2. It is intended 
that spring 174 A, P. 2, shall supply proper tension without 
help from spring 259, P. 2. 

INSTRUCTION NO. 11.—To REMOVE UPPER 
SPROCKET SHIELD, 282 P, P. 1, remove screws (two of 
them) 284 P, P. 1. 

INSTRUCTION NO. 12.—TO REMOVE UPPER 
SPROCKET, 106, P. 4, remove the set screw in the center of 
its hub, and pull the sprocket off the shaft. In replacing it 
remember that the end having an offset hub goes in toward 
the casting. If put on the other way the sprocket will be 
out of line with the aperture, and there will be trouble. 
Having removed the hub you can pull its spindle 51 A, P. 1 


758 


HANDBOOK OF PROJECTION FOR 


and 2, carrying gear 8P. 2, out to the left, first having 
removed the gear cover. (See Instruction No. 1.) 

CAUTION. —In removing upper and lower sprockets you 
must take the set screw clear out before you can pull the 
sprocket off. 

INSTRUCTION NO. 13— TO REMOVE UPPER 



Plate 3, Figure 292. 




















MANAGERS AND PROJECTIONISTS 


759 


SPROCKET IDLER BRACKET, 24, P. 4, remove set screw 
249, P. 4, loosening screws 227 and 265, P. 4. Next remove top 
sprocket, 106, P. 4 (see Instruction No. 12), and you can pull 
the bracket away. 

INSTRUCTION NO. 13^.— IDLER ROLLER, 108, P. 4, is 
held away from the sprocket (see General Instruction No. 
12) by screw 241, P. 4, which is locked by knurled knob, 241, 
P. 4. Idler roller, 108, may be removed from its spindle by 
taking out screw 223, P. 1. We would advise the projec¬ 
tionist to remov the upper, lower and the intermittent idler 
rollers at least once each week, clean and lubricate their 
spindles, using a medium light oil for the purpose. True, 
there is an oil hole in their center, but better take them off. 

INSTRUCTION NO. 14.— LOWER SPROCKET, 106, P. 4, 
may be removed by taking out the screw in its hub and 
pulling the sprocket off the shaft, first having raised the 
idler bracket. If it is desired to remove its spindle, 52 A, P. 
2, which carries take-up belt driving pulley, 20, P. 2, it will 
first be necessary to follow Instruction No. 23. Having done 
so you will see, down in a pocket inside the frame casting, 
gear 17 A, P. 3, which drives the lower sprocket shaft. 
Loosen the set screw in its hub, backing it off a considerable 
distance, as it is deeply countersunk into the shaft, and you 
can pull the driving pulley and spindle out to the left. In 
replacing same be sure you get set screw which holds gear 
17 A, P. 3, properly located in the countersink in the shaft, 
and set it up tight, because if this set screw works loose it 
will be a job to get at it and retighten. 

INSTRUCTION NO. 15.— LOWER SPROCKET IDLER 
BRACKET, 25 A, P. 4, may be removed by loosening the 
screw in the upper end of spring 274, P. 4, and screw 249, 
P. 4, and screw 227, P. 4. In replacing same be sure to 
tighten up screw 227, P. 4, and the one on top of spring 274, 
and to readjust screw 249, P. 4, so that the spring has the 
proper tension. Lower idler roller, 108 A, P. 4, is merely a 
guide roller and sets approximately one-eighth of an inch 
from the sprocket. The other two rollers should, however, 
be adjusted by means of screw 241J4 and lock nut 241, P. 4, 
as per General Instruction No. 12. Any of these idler rollers 
may be removed from their spindle by taking out the screw 
in the end thereof, but it will be necessary to take off the 
entire bracket in order to get the center roller off. 

INSTRUCTION NO. 16.— GEAR BRIDGE, 4 A, P. 3, may 
be removed by taking out screws 224 A (three of them), P. 


HANDBOOK OF PROJECTION FOR 


760 

2. Back these screws out for about one-half inch and then, 
using a screwdriver, carefully pry the bridge away. The 
holding screws are “necked,” in order that they may be left 
in the bridge to avoid the possibility of becoming lost. 
When you have backed them off for about one-quarter inch 
they will release the main casting, though they are still at¬ 
tached to the bridge. In replacing the bridge be sure that 
you get the end of the spindle carrying gear 84, P. 3, properly 
entered in its bearing and also that shaft 50 D, fly wheel 
shaft 61 P, and the pin entering spindle 65, all P. 3, are prop¬ 
erly entered, and that the locating pins enter their proper 
receptacles. Do not attempt to drive the bridge on. If you 
start it right it will enter without any trouble, and all that 
will, in any event, be necessary, will be to tap the casting 
lightly with the handle of the screwdriver immediately over 
each of the two locating pins. 

INSTRUCTION NO. 17.—TO REMOVE REVOLVING 
SHUTTER SHAFT, 197 P., P. 2, remove screws 159, P. 3, and 
158 P, P. 4. You may then pull the spindle and its casting, 
togethe. with the revolving shutter and gear 207 P, P. 3, out. 
Having done this, if it is desired to remove the shutter spin¬ 
dle from the casting, you may do so by loosening the set 
screw in collar, 201 P, P. 3, which will allow you to pull tne 
spindle out of the casting. 

CAUTION.—At either end of the shutter spindle bearing 
is a fibre washer. Be sure and get these washers back in 
place in reassembling. 

INSTRUCTION NO. 18.—TO REMOVE FLY WHEEL 14 
P, P. 2, follow Instruction No. 16, after which remove the two 
set screws in the hub of the fly wheel. It is better to remove 
these screws, as they are deeply countersunk into the shaft, 
then grasping the fly wheel on the other end of the shaft to 
hold it stationary, twist fly wheel 14 P, P. 2, at the same time 
pulling outward, and thus working it off the shaft. 

CAUTION.—In replacing be sure to get the screws proper¬ 
ly located in their countersink. 

INSTRUCTION NO. 19.—TO REMOVE GEAR 87, P. 2, 
take out set screw 129, P. 2, which releases the gear. 

INSTRUCTION NO. 20.—TO REMOVE GEAR 15 A, P. 2, 
follow Instructions Nos. 16 and 17, whereupon the gear may 
be pulled off the spindle. 

INSTRUCTION NO. 21.—TO REMOVE CRANK SHAFT 
50 P, P. 3, first detach the crank, O 13 P, P. 1, then follow In- 


MANAGERS AND PROJECTIONISTS 


761 


struction 20 , thus releasing the shaft, which may be pulled 
out from the left hand or gear side. 

INSTRUCTION NO. 22.— TO REMOVE GEAR 16 P, P. 3, 
follow Instructions Nos. 16, 17, 18 and 20, in their order, and 
then take out screw 16^4 P, P. 3. This releases the gear. In 
replacing be sure that you set up screw 16^ P, P. 3, tight. 

INSTRUCTION NO. 23.— TO REMOVE GEAR 18 A, P. 3, 
follow Instructions Nos. 1, 16 and 18, and then remove screw 
129, P. 3. In replacing be sure to set screw 129 up tight. 

INSTRUCTION NO. 24.— TO REMOVE GEAR 17 A, P. 3, 
follow Instructions Nos. 1, 16, 18 and 23, and then loosen the 
set screw in the hub of gear 17 A, P. 3. Next loosen the set 
screw in the face of belt pulley 20, P. 2, and slip the pulley 



Plate 4, Figure 293 


























762 


HANDBOOK OF PROJECTION FOR 


off its shaft. You may then pull spindle 52 A, P. 2, out from 
the sprocket side thus releasing the gear. 

INSTRUCTION NO. 25.— TO REMOVE AUTOMATIC 
GOVERNOR SHAFT 65, P. 3, and the parts attached thereto, 
follow Instructions Nos. 1, 16 and 18; then, looking in past 
the left-hand edge of the fly wheel, you will see a set screw 
in the hub of a casting in the end of standard 83, P. i. 
Loosen this set screw until the casting will revolve on the 
rod, whereupon you can pull the whole governor away. 
Should it ever become necessary to renew the springs, gear, 
or other parts of the governor, we would advise that it be 
sent to the factory by insured parcel post. Don’t try to do 
this particular job yourself. In replacing the governor the 
set screw in the casting is countersunk deeply into the shaft, 
and it is necessary that this screw enter the countersink, else 
standard 83, P. 1, will not set right, and your automatic fire 
shutter will not work. 

INSTRUCTION NO. 26.— FRAMING CARRIAGE D 1, P. 

4, carrying outside fly wheel, D-38, P. 1, may be removed as 
follows: First loosen screws 216 (two of them), P. 4, and 
then, by means of knurled knob at its top, unscrew framing 
carriage guide rod 72 P, P. 4, and pull it out. Next remove 
the screw which holds the upper end of the link which joins 
the framing carriage and framing lever casting 11 P, P. 4. 
Next loosen the two screws, one at each lower corner of 
the nickel plated shield in the side of the mechanism back 
of the fly wheel, and raise knob 296, P. 1. You may then, by 
working it around a little, pull the whole framing carriage 
out to the right—on the crank side of the mechanism. 

INSTRUCTION NO. 27.— TO REMOVE FLY WHEEL 
SHAFT 61 P, P. 3, follow Instructions Nos. 1, 16, 18 and 26, 
then loosen a set screw in the face of the framing casting 
just behind the lower gate hinge. You will be obliged to 
remove the gate^ in order to get at this set screw. (See 
Instruction No. 5.) This set screw holds the bronze bearing 
in which the shaft runs, and you may then, using either a 
copper or a hard wood punch, drive the shaft bearing and 
inner end of the toggle out into the interior of the frame 
casting. 

INSTRUCTION NO. 28.— STRIPER PLATE D 32, P. 1, 

(F-F, P. 5), may be removed by taking out the three screws 
at its lower end. (See P- 5.) 

INSTRUCTION NO. 29.— FLY WHEEL, D 38, P. 1, may be 

removed by taking out the two set screws in its hub. They 


MANAGERS AND PROJECTIONISTS 


7 63 


are deeply countersunk, and must be backed out for quite a 
distance before the wheel will be released. When the wheel 
is released from the screws, hold the fly wheel on the 
opposite end stationary while you pull the wheel off with 
a twisting motion. 


INSTRUCTION NO. 30.— TO OPEN THE OIL WELL fol¬ 
low Instruction No. 29, and then loosen the screw at each 
lower corner of the nickel plated shield behind the fly wheel 
and remove it; next remove four machine screws in the 
black casting on the end of the framing carriage. These 
screws hold the cover of well E, P. 5, and having removed 
them you can pull the cover off, tapping it lightly to break 
the joint. Before starting this job, you can, if you wish, 
remove the whole framing carriage from the mechanism. 
See Instruction No. 26. It is well to remove the oil well 
cover, say once in each five or six hundred hours running, 
and clean it out thoroughly. 


Never use graphite in the oil well unless you want trouble, 
and plenty of it. 


CAUTION. —In replacing the oil well cover be sure that 
you wipe both the surfaces perfectly clean. If you do not 
there is apt to be a leakage of oil. 


NOTE. —Directions follow for the removal and renewal of 
cam, star and intermittent sprocket and their bushings. We do 
not, however, advise this. It is much better to purchase an 
extra framing carriage, and when anything goes wrong with 
the old one, or when excessive wear develops in the bush¬ 
ings, spindles, intermittent sprocket, or other parts, insert 
the new carriage in the machine and send the old one to 
the factory by parcel post for repairs. It is, of course, pos¬ 
sible that the projectionist can and will make the necessary 
repairs in an entirely satisfactory manner. Still, when one 
considers the delicacy of the parts and the fine adjustment 
necessary, one readily sees that this can be best done at the 
factory, where all necessary tools and men skilled in this 
class of work are available. 

INSTRUCTION NO. 31.— CAM SHAFT X, P. 5, carrying 
cam G, P. 5, may be removed by following Instruction No. 
30, and then loosening the set screws D 13 (two of them) in 
part D 12, P. 4. Back these screws out a considerable dist¬ 
ance, as they are deeply countersunk in to the shaft. Hav¬ 
ing done so you can pull the cam and shaft away, which 
releases part D 12, P. 4. 


764 


HANDBOOK OF PROJECTION FOR 


INSTRUCTION NO. 32.— THE STAR AND ITS SHAFT J. 

P. 5, may be removed by following Instructions Nos. 26, 28, 
and 31. Having done so, take out the two set screws in the 
hub of intermittent sprocket D 10, P. 1, and you can pull the 
star and shaft out. 

INSTRUCTION NO. 33.— TO REMOVE THE BEARINGS 
of the Intermittent sprocket Shaft follow Instruction No. 32. 
The bearing on the star end is held by a set screw, the head 
of which is in the top of the casting, and the bearing in the 
other end is held by a set screw in the face of the casting at 



Plate 5, Figure 294. 

the end of the bearing. Remove these screws and you can 
drive the bearing out and insert new ones. The screws in 
the face of the casting which holds the left hand bearing 
should be set up just far enough so there is no end motion 
in the intermittent sprocket. If you set it tight you will bind 
the sprocket; if you leave it too loose the sprocket is apt 
to have end play. 

INSTRUCTION NO. 34.— THE BEARINGS OF THE CAM 
SHAFT may be removed by following Instructions No. 26 and 






MANAGERS AND PROJECTIONISTS 765 

31. This bearing extends the full length of the casting. It is held 
at one end by a set screw, the head of which is in the top of 
the framing carriage casting; the other end is held by two 
set screws which bear against the lug in the end of the bear¬ 
ing. This bearing is eccentric. Having loosened the two 
set screws which bear against the lug, and the one in the top 
of the casting which holds its other end, you may drive the 
bearing out, using a hard wood punch. In replacing it it 
will be necessary to adjust the bearing carefully. Proceed 
under Instruction No. 35. 

INSTRUCTION NO. 35.— ADJUSTING INTERMITTENT 
MOVEMENT.—When the intermittent sprocket develops 
considerable circumferential play, or the intermittent move¬ 
ment becomes noisy it is in need of adjustment. Proceed as 
follows. Set screws D 26, P. 4, (two of them), bear against 
eccentric bearing lug D 5, P. 4, and a movement of these set 
screws has the effect of altering relation of the star and cam 
to each other. When you loosen the lower screw and 
tighten down on the upper one you tighten the cam against 
the star, thus eliminating the lost motion in the intermittent 
sprocket, but you must be very careful and not get the move¬ 
ment too tight or you will have trouble, particularly if the 
adjustment be done while the machine is cold. Tighten up 
on the upper screw, first having backed off on the lower one, 
until you can feel just the least bit of shake in the inter¬ 
mittent sprocket when you try it with your finger. Having 
got your adjustment made tighten up both set screws. This 
adjustment must be made with the movement “on the lock”— 
in position when the sprocket is locked. 

INSTRUCTION NO. 36.— ADJUSTING THE FRAMING 
CARRIAGE.—The ease with which the framing carriage 
moves up and down is governed by screws 216 (two of them), 
P. 4. Tightening these screws has the effect of pressing to¬ 
gether the casting lug on the guide rod, thus making the 
carriage move harder; conversely loosening these screws 
makes it move more easily. 

INSTRUCTION NO. 37— BEARINGS.—All bearings of 
the Motiograph machine are held by set screws, and may 
easily be removed for replacement. Bearing 194, P. 4, is 
held by set screw 235, P. 4. The bearing which can be seen 
iust at the bottom of gear 207 P. P. 3, is held by set screw 
103 A, P. 4. The bearings in bridge 4 A, P. 3, are held by set 
screws 225 (three of them), P. 3. 


766 


HANDBOOK OF PROJECTION FOR 


INSTRUCTION NO. 38 —OIL.— Never under any circum¬ 
stances use graphite in the oil well. Graphite is ordinarily 

one of the finest lubricants made, but it does not work at all 
satisfactorily in the intermittent movement of a projector, 
nor do we advise its use on gears or on any part of the 
mechanism. We would advise the use of a very heavy oil, 
such as Mobile B, which can be had at almost any garage, 
for the toggle joint. This joint works, under considerable 
pressure, at high speed. If a light oil be used it is likely to 
be thrown off rapidly. Mobile B ought to be about right. 

INSTRUCTION NO. 39-LINING THE SPROCKETS.— 
See General Instruction No. 4. 

INSTRUCTION NO. 40—KEEPING THE SPROCKETS 
CLEAN.—See General Instruction No. 3. 

INSTRUCTION NO. 41.—SETTING THE SHUTTER.—See 
General Instruction No. 22. 

INSTRUCTION NO. 42.—SPROCKET TEETH.—See Gen¬ 
eral Instruction No. 7. 

INSTRUCTION NO. 43.— MOTIOGRAPH TAKE-UP uses 

a flat belt about one-half inch wide. This belt is driven bv 
pulley 20, P. 2, the driven pulley being shown, not attached 
to the mechanism, at 10 A, P. 1. The belt is given the neces¬ 
sary tension by idler pulley 109, P. 1, the tension being gov¬ 
erned by set screw 156, P. 1. This plan is quite efficient, but 
the projectionist should see to it that the adjustment of idler 
109, P. 1, is carefully made, else there will be a heavy pull on 
the film, which is, of course, injurious. 


MANAGERS AND PROJECTIONISTS 


767 


Speed Indicators 

W E have for more than twelve years insisted that there 
is only one proper method of gauging the speed of pro¬ 
jection, viz.: by watching the screen and so regulating 
the speed of the projector that there will be absolute natural¬ 
ness of action in all moving things in the picture. We still in¬ 
sist that this is the fact, but until such time as either some 
method be evolved for automatically synchronizing camera 
speed and projection speed, or projectionists themselves are 
able and willing to concentrate on their work that knowledge 
and extremely close attention necessary to the production of 
naturalness of action, and theatre managers cease compell¬ 
ing the projectionist to run to fixed schedule regardless of 
the time required for proper projection, it is desirable that 
some device be installed in the projection room by means of 
which the exact speed of projection may be constantly under 
the eye of the projectionist. 

In any event, however, a projection speed indicator is de¬ 
sirable if it be rightly used, but the right way of using it is 
to either first project the picture and record the correct 
speed for each individual scene, and thus make a projection 
cue sheet, or for the producer himself to send a cue sheet 
indicating the proper speed of projection for each scene. 

POSSIBLE ABUSES.— The trouble with speed indicators 
is that in present procedure they are often utilized to pro¬ 
duce what amounts to an outrage on projection, because 
often the power is placed in the hands of an orchestra leade. 
to compel the emasculation, or even the absolute butchery 
of artistic work on the screen in order that the music and 
the picture may synchronize without disturbing the tempo 
of the music. Also the theatre manager all too often, with¬ 
out knowing a thing about the speed of projection necessary 
to artistic work in any individual scene, arbitrarily compels 
a speed of projection to accommodate a schedule which may 
be totally unfitted to artistic screen results. The fact that a 
speed indicator is located in his office enables him to compel 
his projectionist to commit an outrage on the production he 
is placing before the audience, and on his own profession as 
well 


768 


HANDBOOK OF PROJECTION FOR 


We cannot, however, ignore a device which has merit, 
simply because that device is abused, or may be abused, 
therefore we are including a description of speed indicators. 

POWER’S SPEED INDICATOR.— The Nicholas Power 
Company has what seems to be a very excellent speed in¬ 
dicator, which may be ordered as special equipment for the 
Power’s Projector. 

This indicator is illustrated in Fig. 294. As will be noticed, 
the upper score indicates the rate of speed per minute at 
which the film is being projected, and the lower score the 
number of minutes required to project a thousand feet of 
film. Examining the two scores, you will see that at 100 
feet a minute it takes 10 minutes to project 1,000 feet of 
film, and at 40 feet a minute it takes 25 minutes to project 
1,000 feet of film. 

In Fig. 295 the various parts of the Indicator are shown. 
With it is supplied a table, A, Figs. 294 and 295, which is 
attached to the projector frame just back of the lower fire 



Figure 294. 





MANAGERS AND PROJECTIONISTS 


769 


shield. This table has an extension, B, Fig. 295, which holds 
the indicator mechanism as per Fig. 294. The indicator head 
is connected to the mechanism by means of an electric circuit 
carried in a conduit, A, Fig. 294. The indicator head may 
be located at any desired place, but it should be beside the 
observation port. There may be a multiplicity of connecting 
circuits, so that one mechanism may be used to operate in¬ 
dicator heads in the projection room, in the orchestra pit and 
in the manager’s office if so desired. The driving power is 
taken from pulley B, Fig. 294, C, Fig. 295, which is a special 
pulley provided with the outfit. You have only to slip off the 
regular projector driving pulley and put on the special one, 
C, Fig. 295. The apparatus is simple, well constructed, and 
will delivej: the goods. 

POWER’S COMBINATION PANEL.— In Fig. 296 we have 
a view of a combination panel put out by the Nicholas 
Power Company. This panel is 10 inches high and 18 inches 
wide. From wall to face it is 4 inches at the top and 7 at 
the bottom, which gives good display to the speed indicator 
(head) the voltmeter and ammeter mounted thereon. 



Figure 295. 





















770 


HANDBOOK OF PROJECTION FOR 


Speed indicators for orchestra pit and manager’s office 
may also be connected to the panel. 

The voltmeter is of the low voltage type, the maximum 
being 75 volts. Inside the panel is an automatic relay which 
automatically disconnects the instrument from the circuit 
when the arc lamp is not in use, thus protecting the same 
from injury by line voltage, even though the projector table 
switch is in. 

An ammeter of any desired capacity can be supplied, and 
shunt for same may be mounted inside the panel, or at any 
desired point on the circuit. When it is located at some 
distant point, as for instance on the back of generator panel, 



Figure 296. 

it is only necessary to run a circuit of No. 14 wires from the 
shunt to the ammeter. 

On the panel is mounted a control switch, the function of 
which is to connect the speed indicator generators to the 
speed indicator units on the panel, so that each projector 
generator is in turn disconnected when the projector is shut 
down, and the generator of the next placed in operation is 
connected by a turn of the switch. The instruments are high 
grade Weston instruments. 

HALLBERG SPEED INDICATOR.— The Hallberg indi¬ 
cator parts are shown in Fig. 297. It is essentially an electric 
device. A small generator of special characteristics is 
mounted on a bracket attached to the projector. The gen¬ 
erator is driven by a pulley attached to the projector mech- 











MANAGERS AND PROJECTIONISTS 


771 


anism. The current from the generator is supplied to a dis¬ 
tribution box located on the projection room panel, or switch 
board, whence it reaches and operates an indicating meter in 
the projection room, one in the orchestra pit and one in the 
manager’s office, if it be so desired. 

Fig. 298 shows the dial of the recorder. On the wall, near 
the lower left-hand corner of Fig. 297, is a recording instru¬ 
ment by means of which a permanent record of speed of pro¬ 
jection is inscribed on a paper dial. This is a valuable feat- 



Figure 297. 






















772 


HANDBOOK OF PROJECTION FOR 


ure of the device in that it makes arguments and disputes 
as to the speed at which any production, or any scene of a 
production was projected impossible. The Hallberg speed 
indicator is a well designed, well-made piece of apparatus. 
It is deserving of consideration by those who propose in¬ 
stalling such a device. 

ROBBIN SPEED INDICATOR.— There is a speed indi¬ 
cator made by Mr. Robbin, New York City. This manufac¬ 
turer was invited, on several occasions, to submit his ap- 



Figure 298. 

paratus for description in this book, or to himself prepare 
matter, subject to our own revision and editing, but he has 
failed to do either of these things, which we believe it will 
be agreed does not evidence very great consideration for the 
many thousands of users of this book, many of whom look 
to it for instruction and guidance in matters pertaining to 
projection room practice and, to a greater or less extent, 
in projection apparatus. 

Mr. Robbin’s speed indicator we understand to be an excel¬ 
lent piece of apparatus of its kind. 








MANAGERS AND PROJECTIONISTS 


773 


The High Intensity Arc 

T HE high intensity arc has several advantages as against 
the ordinary electric arc for projection purposes. Chief of 
these advantages are: (A) the crater faces the collector 
lens squarely, as shown in Figs. 299, 300 and 302. This is an 
advantage because whereas the most efficient angle at which 
the ordinary arc crater could be set to the lens (an angle of 
55 degrees from the optical axis of the lens system) directs 
the strongest light flux toward the lower half of the collector 
lens, instead of its center, the high intensity crater directs 
its strongest light straight toward center of collector lens. 

(B) The intrinsic brilliancy of the high intensity arc crater 
per unit of area is very much higher than is that of the 
ordinary arc crater. The brilliancy of the ordinary arc 
crater when operating with cored carbons is given by Blon- 
del as 132 c. p. per square m. m., but by reason of modern 
improvement in projection carbons this is claimed to be in¬ 
creased to about 160 c. p. 

The high intensity men claim a brilliancy of 500 c. p. per 
square m. m. for their product. We have not as yet verified 
this claim, but certainly the high intensity arc crater has a 
very much higher brilliancy per unit area than has the crater 
of the ordinary arc. That statement'is not a subject for 
questioning. 

(C) The crater area per ampere is decidedly less than that 
of the ordinary arc. By this we mean that a 75-ampere high 
intensity crater, for instance, will have very much less diam¬ 
eter and area than will a 75-ampere ordinary arc crater. 
Exactly how great an advantage this is we are not prepared 
to say, but certainly it is an advantage because it seems 
quite possible to secure all the screen brilliancy any reason¬ 
able man could want without encountering the inefficiency 
under which the ordinary projection arc labors when work¬ 
ing at high amperage. See Pages 396 to 398. 

The point of highest efficiency of the ordinary D C arc 
is about 60 amperes. We believe there would be no ap¬ 
preciable loss in efficiency with the high intensity arc until 
the 100 ampere, or possibly 120 ampere, point was passed. 


774 


HANDBOOK OF PROJECTION FOR 


We recommend the high intensity arc to exhibitors and 
projectionists who desire high screen brilliancy 

COLOR OF LIGHT. —Screens illuminated by the high in¬ 
tensity arc are very brilliant, but the light tone is not, at 
this time (1922) as warm in tone as is the light from the 
ordinary arc. Notwithstanding this phase of the matter, 
which may be corrected later, the public seems to like the 
high intensity screen illumination. We have not heard a 
single theatre patron criticize it adversely, but have heard 
many express approval of the brilliancy of the light. 

THE GENERAL ELECTRIC LAMP.— The General Elec¬ 
tric Company and the Nicholas Power Company, working ip 
conjunction, have developed a high intensity lamp, illustrated 
in Figs. 299 and 300, which same is being put out as special 
equipment by the Nicholas Power Company. Fig. 299 shows 
right-hand and Fig. 300, left-hand side of the lamp. 

In general the operation of the lamp is as follows: The 
carbons, both positive and negative, are fed by a small motor 
located under the base of the lamp. The motor armature and 
field are connected across the arc, which has the effect of 



Figure 299. 




























MANAGERS AND PROJECTIONISTS 


775 


increasing the speed of the motor when the arc length is 
increased and the arc voltage, therefore, increased; or slow¬ 
ing down the motor when the arc gets shorter. This is 
precisely the principle upon which some of the oldest and 
best arc controllers operate and its application to this lamp 
should maintain the arc automatically with but very little 
attention. Knob Q and crank R, Fig. 299, are for the pur¬ 
pose of feeding the carbons by hand, when, or if, necessary. 

The positive carbon is pushed through an opening in tube 
A, Fig. 299, and shoved through clamp E and positive contact 
shoes H, until its tip extends 9/16 of an inch as per Fig. 301. 

The carbon is held by clamp E, Figs. 299 and 300, which 
clamp engages with feed screw M, Fig. 300. Positive carbon 
clamp E is insulated so that no current can enter the carbon 
through the clamp. This prevents the carbon heating by 
having current forced through its entire length, it also pre¬ 
vents positive feed screw M and negative feed screw L, 
Fig. 300, from carrying current which might cause disastrous 
arcing between the clamp and feed screw. 



Figure 300. 








































776 


HANDBOOK OF PROJECTION FOR 


CURRENT ENTERS THE CARBON.— Current is con¬ 
ducted to the positive carbon through the floating contact 
shoes, shown at H, Figs. 299 and 300. These contact shoes 
are held in contact with the; carbon by the action of a coil 
spring and are so arranged that they may make a firm and 
even contact with the carbon at all times. 

The current enters the negative carbon through carbon 
clamp F, Figs. 299 and 300. Current is supplied to this clamp 
through flexible wire jumper, shown at 3, Fig. 300. The nega¬ 
tive carbon is a metal coated carbon and the current is con¬ 
ducted from the clamp through the full length of the carbon. 
Both the negative clamp F and the positive carbon clamp H 
are insulated from the body of the lamp. This is illustrated 
in Fig. 302, the dotted line representing the path followed 
by the current through the lamp. 


POSITIVE CARBON ROTATED.— From Q to P, Figs. 299 
and 300, the parts form one assembly. Looking at Fig. 300, 
between the arrowheads 14 and 15, you will see directly in 

front of gear 
to which arrow 
14 is pointing, 
a casting 
which forms 
one end of the 
support for the 
positive carbon 
carriage. The 
other end of 
this carriage is 
supported by a 
similar casting 
between 
arrows H and 
P, directly be¬ 
ll i n d positive 
contact shoes 
H and asbestos 

baffle plate. This carriage, including part A and Knob Q, is 
continuously rotated by the motor, carrying with it, of course 
the positive carbon, as well as feed screw M and clamp E, 
both of which are mounted on the carriage. The rotation of 
the positive carbon maintains at all times a perfectly round 
and symmetrical positive crater. 

The positive carbon is not fed continuously, but intermit- 



Figure 301. 
























MANAGERS AND PROJECTIONISTS 


777 


tently. This is accomplished as follows: On the rear end of 
positive feed screw M, a ratchet wheel is mounted, indicated 
by V, Fig. 300. On the stationary frame of the lamp, U, Fig. 
300, is a spring pawl and every time the positive carbon 
carriage rotates, this pawl engages the ratchet and pulls it 
and the positive feed screw around slightly. 

Adjustment screw T, Fig. 300, is provided to enable the 
projectionist to regulate the rate of feed of positive carbon. 

SAFETY CLUTCHES. —The motor is directly connected, 
through gearing, to the feeding mechanism and there is pro¬ 
vided, both as a safety device and to enable the projectionist 
to feed the carbons by hand without disconnecting the 
motor, a spring pressure friction clutch, which is placed on 
both the positive and negative feed rods. They are indicated 
at S, Fig. 300. The gear at the front end of the clutch is not 
connected to the shaft but rotates loosely thereon. It is 
held, or gripped, between two collars, one of which, the one 
between the support bearing and the gear, is attached to the 
feed shaft and must rotate therewith. The pressure is ap¬ 
plied by a coil spring which rests against the collar which 
rotates loosely with the gear. This pressure can be adjusted 
by tightening or loosening the hexagon lock nut on which 
arrowhead S is resting. By examining this construction, you 
will see that if crank R is turned with sufficient force, the 
feed rod will be rotated although the gear must remain sta¬ 
tionary or may be running with the motor. When crank R is 
rotated, the friction supplied to the clutch by the coil spring 
is overcome and the carbons are thus fed by hand, regardless 
of whether or not the motor is running. 

These clutches act as safety devices as follows: If either 
the positive or negative carbon be burned too short, the 
positive clamp E will strike the front of the carriage at P, 
Fig. 300, or negative clamp F will strike the negative head at 
O, Fig. 299. When this happens the feed screw could feed 
the clamp and carbon no further and the motor would in¬ 
stantly be stalled with probable serious injury to its arma¬ 
ture. In that event, however, the clutches operate and allow 
the motor to continue running although under heavy load. 

HAND FEEDS WORK HARD.— For the reason that in 
order to operate the hand feeds the clutches must be slipped, 
these feeds work hard. 

NOTE.—The-pressure of the springs operating the clutches 
must be sufficient to enable the motor to drive the feeding 
mechanism, but not so great that the feeding mechanism will 


778 


HANDBOOK OF PROJECTION FOR 


work unnecessarily hard, or that the motor will be stalled if 
one of the clamps strikes, as before described. 

THE NEGATIVE CARBON is fed upward by feed screw 
L, acting through carbon clamp F. The feeding is not in¬ 
termittent but continuous. The negative is not rotated. It 
may be fed by hand by means of crank R, Figs. 299 and 300. 

INSTALLATION. —The lamp is installed in the lamphouse 
by the manufacturer, the lamp and lamphouse not being sold 
separately for an original installation. It is so adjusted by 
the manufacturer that the center of the positive carbon is 
exactly on the optical axis of the lens system. It is, how¬ 
ever, possible that the adjustment may be altered in ship¬ 
ment, or it may be that you will have occasion to order a 
new high intensity lamp to install in place of an old one. 



On receipt of a new high intensity outfit, or when you in¬ 
stall a new lamp in the place of an old one, you should set the 
alignment of the lamp, as follows: Secure a perfectly 
straight rod of steel or iron having the same diameter as 
the positive carbon (11 m.m. or about 7/16 of an inch) 
and long enough to reach from an inch or more back of knob 
Q to the front of the projection lens tube. Test the rod for 
straightness by rolling it on a perfectly flat surface. Re¬ 
move the condenser lenses, open the projector mechanism 
gate, and take out both combinations of the projection lens, 
placing the empty lens barrel back in place in the holder. 
Remove the positive carbon and shove the iron rod through 











































































MANAGERS AND PROJECTIONISTS 


779 


tube A, clamp E, positive contact shoes H and on through the 
aperture and lens barrel. If the rod is exactly central with the 
aperture (use an inside calliper for measuring) and with the 
front end of the projection lens barrel, all is well. If not, 
then loosen nuts B B, Fig. 299 (four of them) and adjust nuts 
C C, Fig. 299 (four of them) until the rod is centered up and 
down and nut D, Fig. 299, until it is centered sidewise, after 
which tighten nuts B B down solidly. 

NOTE.—It is possible to make a very good adjustment by 
merely centering the end of the rod in the aperture, but 
when it is centered with both the aperture and lens barrel 
we know it is exactly right. 

CURRENT STRENGTH.— The General Electric Company 
builds its lamps to operate at a certain definite amperage 
and voltage. If you want the best results do not depart 
therefrom. If you do depart therefrom and trouble and dam¬ 
age to the apparatus results, do not blame anyone but your¬ 
self. 

There are those who think that because they can operate 
an ordinary arc lamp at almost any desired amperage, they 
can do the same with the high intensity lamp. If you have 
any such idea you had better revise it, and come to an under¬ 
standing of the apparatus you are handling. If your lamp is 
rated at 75 amperes and 60 volts, that amperage and voltage 
must be maintained for best results, though no serious dam¬ 
age will follow if the amperage does not run above 80 or drop 
below 70. 

CARBONS. —Under no conditions attempt to use any other 
than high intensity carbons. Positive high intensity carbons 
are 11 m. m. (about 7/16 inch) in diameter by 18 inches long. 
Negatives are 11 m. m. by nine inches long, bevelled at one 
end. The General Electric Company recommends the use 
of National Carbon Company’s High Intensity carbons. 

NOTE.—In ordering carbons always give rated capacity of 
lamp. 

INSTALLING NEW CARBONS.— By means of Knob Q 
move the positive carbon clamp E back as far as it will go 
and by means of crank R, move negative carbon clamp F 
down as far as it will go. Put negative carbon in first, push 
it through negative bafle plate G and down through clamp F 
until only about one inch of the tip remains above the face 
of the negative bafle plate G, as shown in Fig. 301- Tighten 
the screw of clamp F until the clamp grips the carbon firmly. 
Next shove the positive carbon through tube A, clamp E and 
positive contact shoes H, relieve the pressure of contact 


780 


HANDBOOK OF PROJECTION FOR 


shoe by raising up slightly on the end of pressure arm so 
that carbon will slip through contact shoes H easily. Shove 
the carbon through until you have its tip as per Fig. 301. 
Tighten the screw in clamp E and the job is finished. 

CAUTION. —Clamp E must grip the carbon tightly enough 
to carry the carbon forward against the friction of the con¬ 
tact shoes. 

CAUTION. —While the carbons are long enough to run 
several reels, it is best, after each reel, to loosen clamps E 
and F and by means of Knob Q and crank R, bring them back 
to the end of their travel. Should you be caught without suffi¬ 
cient carbon to finish a reel (always supposing there is 
sufficient carbon in the lamp but that clamps E and F have 
fed forward as far as they will go) you can, by acting quickly, 
loosen the clamp screw and pull the clamp back while the 
arc is burning. This is, however, poor practice and if you 
run the clamp back after such reel you will not be com¬ 
pelled to resort to it. 

DISTANCE CRATER TO FACE OF COLLECTOR LENS. 

—This will be a matter for experimental determination. Due 
to the difference in crater area per ampere and to the pos¬ 
sible difference in heat of the crater, it will not be found 
practical to use the lens tables compiled for the ordinary 
arc. As the matter now stands we would advise you to 
determine what minimum distance you can carry your high 
intensity arc from the lens without undue breakage, and then 
use a 6.5 inch focal length collector lens and whatever focal 
length converging lens will give you the correct spot. This 
matter presents a problem which will have to be worked out. 
Watch the Projection Department. Data will be published 
therein as soon as possible. 

OPERATION.— To strike an arc, first close the lamp 
motor switch. Next turn the negative hand adjustment 
crank R until negative is raised sufficiently to make contact 
with the positive, whereupon immediately separate the car¬ 
bons, thus forming the arc. Now lower the negative until 
proper arc length is reached as per Fig. 301. Unless the arc 
length varies considerably no further attention will be neces¬ 
sary during the running of the reel, but if one carbon burns 
faster than the other, then hand adjustment will be required 
to re-establish proper arc length as per Fig. 301. 

Should the positive carbon regularly burn away either 
faster or more slowly than the negative then an adjustment 
of the ratchet and pawl, which control the rate of feed of 


MANAGERS AND PROJECTIONISTS 


781 


the positive carbon, should be made. This may be accom¬ 
plished by loosening lock nut on set screw T, Fig. 300. Should 
the positive carbon be feeding too slowly, a turn of the set 
screw T toward the right, or in a clockwise direction, will 
cause the pawl to engage more of the teeth on the ratchet 
and in this way feed the positive carbon a greater distance 
for each revolution of the carriage. Should the positive car¬ 
bon be feeding too rapidly, by turning screw T in a counter¬ 
clockwise direction, the reverse action from the above will 
take place. This pawl U, Fig. 300, should be adjusted until 
the proper rate of feed of the top carbon is established, after 
which lock nut on set screw T should be tightened. If this 
lock nut on set screw T should become loose, set screw T 
may be turned out of its correct position by the pressure 
applied to feed ratchet and pawl U during the operation of 
the lamp. 

SHOULD THE POSITIVE CARBON AT ANY TIME 
FAIL TO FEED examine the ratchet and pawl adjustment 
and make sure that at each revolution of the carriage the 
ratchet engages with the pawl and that the ratchet is turned. 
Should this not be at fault, examine clamp E, making sure 
that the carbon is gripped tight enough to force it forward 
against the pressure of the contact shoe. 

NOTE—Hand adjustment knob Q and crank R will work 
hard when turned by hand because to turn them you must 
overcome friction of clutches S, Fig. 300, and cause them to 
slip against the pressure of the tension spring thereon. 

LAMPS IN SERIES. —High intensity lamps may be oper¬ 
ated from a series type motor generator, exactly as are the 
ordinary projection arc lamps. The procedure, wiring, etc., is 
exactly the same. 

HIGH INTENSITY A. C. OPERATION.— In case of emer¬ 
gency the G. E. High intensity lamp may be operated on A. C. 
In case your D. C. current supply should from any cause fail, 
first, since the lamp motor is a D. C. motor, disconnect it from 
all current supply. You may then connect the lamp to A. C. 
supply, either through an inductor, economizer, A. C. com- 
pensarc or any other similar low voltage transformer or 
through a suitable rheostat using the same carbons if the A. C. 
operation is to continue for but a few moments. If. however, 
you are to use A. C. for more than a few moments, then install 
a short high intensity positive carbon instead of the regular 
high intensity negative. 


782 


HANDBOOK OF PROJECTION FOR 


CAUTION.— Do not use the full rated D. C. amperage of 
A. C. About 3/4 the rated D. C. amperage is as much as you 
should use of A. C, which means that a lamp rated at 75 am¬ 
peres D. C. should only be allowed 60 to 65 amperes A. C. 

KEEP CLEAN.— Both the positive contact shoes H and 
also the opening in the asbestos baffle plate, directly behind 
them, should be kept clean and free from carbon dust. The 
contact surfaces on the positive contact shoes should be in¬ 
spected every day. This may be done in the following 
manner: 

Remove the screw holding the flexible metal ribbons, 5, Fig. 
300, to the positive terminal, after which separate the arms 
sufficiently to release the coil spring and the entire positive 
shoe assembly can be lifted off the studs supporting it and 
thoroughly cleaned. The opening in the asbestos baffle plate 
should be kept clear and free from carbon particles. 

The negative assembly does not require a great amount of 
attention, although care should be taken that the opening 
in the asbestos baffle plate G, Figs. 299 and 300, be kept clean 
and open so that the carbon may pass freely without binding. 
Care should also be taken that the negative carbon clamp F 
makes good contact with the carbon at all times. 

EXAMINE TENSION. —Examine tension of positive cur¬ 
rent carrying contact shoes at least once, and preferably 
twice, a day. Tension must be sufficient to give firm contact 
and prevent arcing between carbons and clamp. Excess 
tension puts unnecessary strain on the motor and the carbon 
feeding mechanism; also it compels you to set clamp E 
unnecessarily tight. 

THE MOTOR. —Motor brushes should be inspected at least 
every month; every two weeks, would be better. Use a good 
grade of machine oil in motor cups. 

SPARE PARTS. —To guard against possible trouble and 
vexation, we would advise the projectionist to carry in stock 
the following spare parts: One positive contact shoe as¬ 
sembly, complete, shown at H, Fig. 300, for each lamp. One 
positive carbon clamp, shown at E, Fig. 300, for each lamp. 
One negative carbon clamp, shown at F, Fig. 300, for each 
lamp. One flexible wire jumper, shown at 3, Fig. 300, for 
each lamp. An extra pair of motor commutator brushes, for 
each lamp. 

These parts are not expensive and they will be in the 
nature of insurance against possible trouble See page 869. 


MANAGERS AND PROJECTIONISTS 783 

IMPORTANT NOTE: Full description of the Simplex High 
Intensity Arc Lamp, manufactured by the Precision Machine 
Company, Inc., will be found on pages 586 to 591 inclusive. 


THE SUN-LIGHT AUTOMATIC HIGH INTENSITY LAMP 

The complete Sun-Light automatic high intensity pro¬ 
jection lamp has been designed in two separate units, 
viz.: the lamp unit and the automatic control unit. The 
lamp unit is shown in Fig. 303, and the automatic units in 
Figs. 304 and 305, which are respectively views of opposite 
sides of the unit. 

The lamp unit consists of the adjustable mounting, or base 
and the carbon holders, contacts and the screws which feed 
the carbons. This entire unit is what the projectionist would 
term “the lamp.” The adjustable mounting, or base is a simple 
arrangement—so arranged that by its manipulation the posi¬ 
tion of the arc crater may be changed, either up, down or side- 
wise. It consists of three main castings, viz.: the base, 5-201, 
Fig. 303; the swivel stand, 5-202, Fig. 303; and the lamp sup¬ 
porting bracket, 5-203, Fig. 303. 

Base 5-201 is mounted on a coarse threaded screw by means 
of which the entire lamp may be moved backward or forward, 
thus altering distance of crater from lens. Swivel stand 5-202 
is turned on its axis by screw 5-207, which connects with an 
adjusting handle or knob outside the lamphouse, as do all the 
other adjustment screws. This action moves the crater side- 
wise with relation to the lens. 

Adjusting screw 5-210 raises or lowers the front end of the 
lamp by swinging lamp supporting casting 5-203 on the hinges 
formed by screws 5-211, Fig. 303. 

The lamp proper is insulated from the base or adjustable 
mounting by means of an asbestos plate, 5-216, Fig. 303. 

The main frame of the lamp, 5-1, Fig. 303, carries all the 
lamp parts, both positive and negative. The fact that the only 
contact between any part of the lamp and its base is at 5-216 
reduces chances of grounding, because it is unlikely any ob¬ 
ject will come into contact with anything but the base. 

On account of the high amperage and relatively small size 
of positive carbon, it would cause excessive heating to force 
the currrent through the entire length of the carbon. It has 
therefore been so arranged that the current enters the posi- 


784 


HANDBOOK OF PROJECTION FOR 


tive carbon through a heavy metal contact, 5-3, Fig. 303, the 
front edge of which is within 3/4 of an inch of the crater. 
This contact is held to the carbon by means of a metal shoe, 
5-4, Fig. 303, by spring 5-5, Fig. 303, the action of which will be 
described further along. It is of the hairpin type (see Fig. 
303J4) and is located well away from any heat which could 
do it injury. 

The positive carbon is held, or gripped in clamp 5-43 by 
means of screw 5-44, which bears directly on the carbon. It 
has a wide, flat point, but be careful and do not set down too 
tightly. If you do you may crush the carbon. It is not nec- 



Figure 303. 


essary to set the screw very tight, since the only office of the 
clamp is to carry the carbon forward against the friction of 
contact 5-4. 

This carbon clamp, or holder is a hollow shaft on which is 
attached gear 5-41, which retains the holder in its bearing 
5-39, the whole being a part of positive carbon carriage 5-39, 
which includes the casting riding on positive feed screw 5-35 
and rod 5-31. Gear 5-41 and clamp 5-44 rotate together, as 
one part, with part 5-39 acting as a bearing for the shaft they 
ride on, the whole being shoved ahead or pulled back by feed 
screw 5-25. All numbers refer to Fig. 303. 









MANAGERS AND PROJECTIONISTS 


785 


We have tried to make this very clear because it is essential 
that you understand the action of the carriage in order that 
you may understand the other details. 

The positive carbon is rotated semi-continuously by gear 
5-41, which is itself driven by a small gear immediately under 
it, 5-50, Fig. 303. This latter gear is carried along rod 5-31 
as the carbon carriage moves forward, but it makes positive 
driving contact therewith by means of a slot in the shaft into 
which a key in the hole of the gear fits; shaft 5-31 being 
rotated semi-continuously by means of ratchet 5-121, Fig. 304. 
The reason we say the rotation is semi-continuously is that 
while the action is to all intents and purposes continuous, 
still it is accomplished by means of pawl 518, Fig. 304, acting 
on its ratchet, hence it is not a strictly continuous movement. 
The feeding forward of the positive carbon is by means of 
a coarse threaded screw 5-35, which moves the whole posi¬ 
tive carbon carriage forward, or pulls it back when necessary 
The feeding of the positive carbon is not continuous, but is 
automatic and intermittent. The feed is designed to main¬ 
tain the crater in a position, the possible variation from which 
is fixed within certain very definite and very small limits. 

THIRD ELECTRODE. —The position of the positive crater 
and the feeding of the positive carbon to the arc is accom¬ 
plished by a “third electrode” system, the main element of 
which is numbered 5-15, Fig. 303. The third electrode, 5-15, 
is a ribbed casting of a heat resisting metallic alloy. It is 
mounted just over the front end of the positive carbon, and 
is insulated from both positive and negative parts of the 
lamp. This later is accomplished by means of bracket 5-8, 
Fig. 303, which is insulated by material 5-11, Fig. 303. 

HOW IT WORKS.— By means of screw 5-13, Fig. 303, the 
third electrode may be shoved ahead or retarded, and it is 
the position of the front tip of the third electrode with rela¬ 
tion to the tip or end of the positive carbon which determines 
the position of the crater, or in other words, its distance from 
the face of part 5-3, Fig. 303. If part 5-15 be moved further 
out, then the crater will form further out, or vice versa. Part 
5-15 should be so adjusted that the crater will form about 3/4 
of an inch from the face of part 5-3, Fig. 303. 

CAUTION.— After making an adjustment of the position of 
part 5-15 always tighten lock nut 5-14. 

From part 5-15 an asbestos covered wire extends back to 
terminal 5-19, which connects with the automatic unit control, 
the operation of which will be described further along. 


786 


HANDBOOK OF PROJECTION FOR 


The feeding of the positive carbon is accomplished through 
the third electrode as follows: When the arc is burning nor¬ 
mal, with the crater in its proper position, the flame from 
the arc does not touch the third electrode, but shoots up past 
it. As the crater burns back, however, the flame, which is a 
fairly good conductor of electricity, touches the face of the 
third electrode. This completes a circuit, energizes a magnet 
and sets the automatic unit to work feeding the positive car¬ 
bon forward until the flame is out of contact with the face 
of the third electrode, whereupon the circuit is broken and 
the positive carbon feeding instantly stops until contact is 
made again between the face of the third electrode and the 
flame. 

The action of the automatic unit in this respect will be ex¬ 
plained in detail further along. 

THE NEGATIVE carbon is at an angle of 45 degrees to the 
positive, which latter lies horizontal. The negative is not ro¬ 
tated, but is fed up to the arc by means of a coarse threaded 
screw located just back of screw 5-35, Fig, 303, which acts 
through connecting rod 5-58, Fig. 303. Rod 5-58 connects 
negative carriage 5-59 with the feed screw through hinge joint 
5-56, of which screw 5-57 is the hinge pin. The hinge is nec¬ 
essary because the feed screw lies horizontal, and pulls 5-56 
along horizontally, while negative carriage is pulled up at an 
angle. Feeding of the negative is by means of ratchet 5-120, 
Fig. 304. It will be described under “the Automatic Control 
Unit.” 

Screw 5-57 and part 5-52 with which it connects (which 
rides on the feed screw) are insulated from part 5-56 and con¬ 
necting rod 5-58. 

The negative carriage slides up and down on two round 
rods, one of which is numbered 5-68, Fig. 303. Set screw 
5-64 clamps the negative carbon in its holder, or clamp. This 
screw should be kept well lubricated with graphite. The nega¬ 
tive carbon carriage is hinged at its bottom, screw 5-61 being 
the hinge pin, which allows spring 5-62, Fig. 303, to pull the 
upper end of the carbon down into current carrying contact 
5-67. Both carbon clamp 5-63 and contact 5-6 7 carry current, 
and in emergencies either may carry all the current, though 
to avoid excessive heating of the carbon it is intended that 
the upper contact carry most of the current. It is therefore 
essential that you keep contact 5-67 perfectly clean, and that 
you test the tension of spring 5-62 frequently. Every time 
you put in a new negative is none too often. Test by pull- 


MANAGERS AND PROJECTIONISTS 


787 


ing the top of negative outward to raise it out of contact 
5-67. You will soon learn to judge whether the tension is 
right or not. 

YOU SHOULD HAVE EXTRA SPRINGS, and if you find 

a spring is getting weak, or has lost its temper, remove nega¬ 
tive carbon and take out hinge screw 5-61, Fig. 303. You may 
then lift negative carbon holder off top end of spring and, 
using a screw-driver, pry the tip of the spring out of the 
casting, insert the tip of the new one and reassemble the 
parts. The whole operation should not consume more than 
from three to five minutes. 

Contact 5-67 also serves the purpose of keeping negative 
carbon always in perfect alignment. 

Care should be taken to sweep top of insulating material 
5-85, Fig. 303 clean every day. Do not allow dirt or carbon 
dust to accumulate on any insulating material, or elsewhere 
for that matter. 

The entire negative carriage may be removed from the lamp 
by taking out two hexagon headed bolts, one of which is 
part 5-70, Fig. 303, removing screw 5-66 to disconnect strap 
5-65, and disconnecting lower end of rod 5-58, Fig. 303. 

NOTE.—You should have an extra current carrying strap 
5-65. You may not need it, but since the strap is subject to 
constant movement it may, in course of time, give way. 

CLEAN POSITIVE CONTACT —Positive contact 5-4 
should be removed occasionally and thoroughly cleaned and 
examined. To do this, first loosen the screw at lower end of 
current-carrying strap 5-6, Fig. 303. Next remove lock nut 
5-14 from the stem of third electrode 5-15, Fig. 303, and re¬ 
move the third electrode itself by screwing stem 5-13 out of 
bracket 5-8, Fig. 303. 

Next, with the right hand grasping spring 5-5, compress it 
and, using a screw driver, pry the loop at its upper end off 
of ear A, Fig. 303 and take the spring out. This releases 
all the parts, w f hich may be lifted out, inspected and cleaned. 
First lift off part 5-4, Fig. 303, which is loose-hinged at its 
left hand end. You may then lift out part 5-3. 

NOTE.—When you have part 5-3 out you will note at its 
lower end a V-shaped recess in the main frame of the lamp, 
into which part 5-3 fits. Examine carefully and make sure 
there is no arcing between part 5-3 and the frame. If there 
is it is evidence that current-carrying strap which connects 
at its lower end to the lower end of part 5-3, is not making 


788 


HANDBOOK OF PROJECTION FOR 


good electrical contact. Clean the parts thoroughly and ex¬ 
amine both contacts of the strap, locate the trouble and fix 
it. 

CAUTION. —Reassembling is but the reverse of the process 
of disassembling, just described, but be carefully to tighten 
nuts of current carrying strap 5-6 down firmly. 

The end of spring 5-5, Fig. 303, indicated at B, should set in 
the small ear on the side of contact piece 5-3. The form of 
this spring is shown in Fig. 303J4. Between part C and the 
front wall of D is a recess, up through which the long end 
of the spring passes, its upper end hooking over an ear on 
the end of part 5-4 at A, Fig. 303. 

NOTE.—Should the projectionist be so careless as to allow 
the positive carbon to burn away until the front end of posi¬ 
tive carbon carriage strikes the frame of the lamp at C, Fig. 

303, while the motor will not 
be stalled because of spring 
5-37, which enables the motor 
to keep running, still it is pos¬ 
sible the crater will then burn 
back far enough to burn away 
the tip of third electrode 5-15. 
In case it does, however, you 
may still secure perfect arc 
regulation by advancing the 
third electrode until its face 
occupies the position necessary 
to maintain the crater the 
correct distance from part 5-3. 
In other words, the third electrode will work without the tip, 
but you will have to set it further forward. 

IN EMERGENCY. —Such a thing should never happen, and 
never will happen if proper care be exercised, still in event a 
reel is started with a positive too short to finish it, it is pos¬ 
sible to “get by” as follows : Loosen screw in clamp 5-44, 
Fig. 303, and insert a new positive carbon behind the old one. 
Now, by hand, very carefully shove the carbon in, pushing the 
old one ahead just enough so that the flame clears the third 
electrode and the crater is kept in its approximately proper 
position. This will take very careful work, but it can be 
done. Understand that this is only to be done in case of genu¬ 
ine emergency, when the projectionist has miscalculated and 
has not sufficient positive carbon to finish a reel. 



Figure 303^2. 










MANAGERS AND PROJECTIONISTS 


789 


SPARE PARTS. —You should carry the following spare 
parts for the lamp. None of them is expensive. 

One current carrying strap 5-65, Fig. 303. 

Two springs 5-5, Fig 303. 

Three or four springs 5-62, Fig. 303. 

One third electrode for each lamp, 5-15, Fig. 303. 

One each 5-3 and 5-4 for each lamp. 

Half a dozen screws 5-45, Fig. 303. 

Set insulating tubing and washers,-5-17, Fig. 303. 

THE AUTOMATIC UNIT PANEL.— In considering Figs. 
303 and 304 let it be understood that universal joints 5-34 (3 
of them) Fig. 303, connect respectively to 5-120, 5-121 and 
5-119, Fig. 304. 

The automatic control unit is shown in Figs. 304 and 305, 
they being views of opposite sides, Fig. 304 having the mech¬ 
anism cover, 5-102, removed. The control is mounted on 
the outside of the back of the lamphouse. The unit contains 
the driving motor and all the mechanism for feeding the car¬ 
bons, rotating the positive carbon and automatically main¬ 
taining the crater of the arc in the required position. 

Motor 5-104, Fig. 304, supplies all necessary power. It runs 
continuously and on arc voltage. The motor armature shaft 
is coupled, by means of spring coupling 5-105, Fig 305, to a 
worm and worm gear mounted in worm gear housing 5-108, 
Fig. 305. Access to gears may be had by removing screws 
5-139 and cover 5-109, Fig. 305. The small cap 5-110 should 
be removed occasionally for inspection and the repacking of 
the worm with grease. Use good grade automobile grease 
for this purpose. On the other end of its shaft the worm gear 
carries crank 5-113, Fig. 304, and it is this crank which feeds 
both carbons and rotates the positive. The crank rotates at 
the rate of about 100 revolutions a minute, or approximately 
three times around in two seconds. 

The slot in the upper end of upper arm of rocker arm 5-114 
Fig. 304, engages with the pin on crank 5-113, therefore, since 
the rocker arm is pivoted on a stud, the cap screw of which 
is numbered 5-115, Fig. 304, it follows that when the crank 
revolves the rocker arm will swing, or rock, and since pawl 
5-117 is attached to its left-hand end and pawls 5-118 and 
5-116 are attached to its right-hand arm, these pawls will be 
lifted up and down with each revolution of the crank. 

Pawl 5-118 is held in continuous engagement with ratchet 
5-121 by means of coil spring 5-126 and ratchet 5-121 is con¬ 
nected, by means of a square shaft, with shaft 5-31, Fig. 303, 


790 


HANDBOOK OF PROJECTION FOR 


which is the shaft which drives gear 5-40 and 5-41, Fig. 303, 
which same rotate the positive carbon. The rotation of the 
positive carbon is, therefore, to all intents and purposes con¬ 
tinuous, as long as the motor runs. 

Pawl 5-116 is held just out of engagement with ratchet 
5-119, which ratchet connects with positive carbon feed screw 
5-35, Fig. 303. The positive carbon, therefore, will not be fed 
until some agency pulls the pawl into engagement with the 



Figure 304. 

Automatic Control Unit with Cover Plate Removed. 
























MANAGERS AND PROJECTIONISTS 


791 


ratchet, and here is where the third electrode steps in. 
When the crater burns far enough back that the flame 
strikes the third electrode, as already set forth, a circuit is 
completed through the flame, which energizes magnet 5-130, 
which causes armature arm 5-134, Fig. 305 to pull pawl 5-116 
into engagement with the ratchet and since the pawl is being 
continuously lifted up and down the ratchet is rotated and 
the positive carbon is fed forward until the flame is out of 



Figure 305. 

Automatic Control Unit—Back View. 












792 


HANDBOOK OF PROJECTION FOR 


contact with the third electrode, whereupon the feeding 
stops, to be automatically begun again as soon as the flame 
again strikes the third electrode and thus re-energizes the 
magnet. 

The feeding of the negative carbon is controlled by the 
arc voltage, and is entirely independent of the feeding of the 
positive carbon. The effect of positive carbon control is to 
maintain the crater in a fixed position, and the effect of volt¬ 
age control of the negative feed is to automatically maintain 
a certain, fixed arc length. Both of these are good. The 
negative feed works as follows. The magnet controling the 
negative carbon feed is numbered 5-131, Fig. 105. One of its 
terminals is attached to the positive and the other to the 
negative side of the line near the lamp. In addition to this 
connection, which is in the nature of a shunt, the magnet 
frame itself carries a few turns in series with the arc, num¬ 
bered 5-155, Fig. 305, composed of heavy asbestos covered 
wires. This series winding acts as a compensator for 
changes in current at the arc, hence has the effect of main¬ 
taining a fixed arc length, regardless of current fluctuation. 

The method of operation is as follows : As the negative 
carbon is consumed the arc becomes longer, hence the arc 
voltage is increased. This increases the pull of magnet 
5-131, which causes magnet arm 5-132, Fig. 305, to move over, 
carrying with it pawl 5-117. Fig. 5-304, to which it is attached 
by connecting bar 5-127, Fig. 304, until the pawl comes into 
contact with ratchet 5-120, which connects to negative car¬ 
bon feed screw 5-47, Fig. 303, and since the ratchet will thus 
be rotated the negative carbon will be pulled upward until 
the arc is shortened, and its voltage thus decreased until the 
magnet no longer has sufficient energy to hold the pawl in 
contact with the ratchet, whereupon feeding automatically 
stops until the process is repeated. 

The arc voltage may be adjusted at any desired value by 
means of tightening or loosening knurled knob 5-150, Fig. 
305, which is held to the main plate by screw 5-151. Twisting 
knurled knob 5-150 increases or decreases the tension of a 
coil spring, not shown in illustration, according to the way 
it is turned. Increase of tension increases length of arc and 
vice versa. 

GAUTJON.—This adjustment is very sensitive. The knob 
should be turned just a very little at a time, and its effect 
noted. Any considerable turn will throw the adjustment 
clear out and probably cause considerable trouble before 
you get it right again. 


MANAGERS AND PROJECTIONISTS 


793 


The claim of the manufacturer is that the control is such 
that both the positive crater and the tip of the negative car¬ 
bon will be kept within 1/32 of an inch of their fixed posi¬ 
tion for an entire trim of carbons, without any attention on 
the part of the projectionist, and with no possibility of the 
positive crater working slowly out of position. 

HAND FEED. —Both the rotating shaft and both carbon 
feeds have auxiliary hand feed controls, so that the lamp 
may at any time be operated by hand. By moving small 
slide bar 5-125, Fig. 304 to the left, both automatic carbon 
feeds will be cut out by stops on the slide bar which hold the 
feed pawls out of engagement with their ratchets. 

CAUTION. —After striking the arc, and before you do any¬ 
thing else, be sure the slide bar is pushed to the right, and 
that the automatic feeds are functioning properly. If the 
automatic feeds are cut out and the projectionist does not 
feed the lamp by hand, damage may and probably will be 
done to the tip of the third electrode by the burning of the 
positive crater back under it. 

The automatic control unit is attached to the lamphouse by 
means of three screws, one of which is in stud 5-128, Fig. 
305, and the other two in the holes in the cross plate just 
above the motor, Fig. 305. 

Cover 5-102, Fig. 304, attaches by means of four screws. 
The three springs beside the cover slip over the ratchet 
hubs, hold them in their bearings and supply enough friction 
that the ratchet will not be dragged backward by the reced¬ 
ing pawls. 

In replacing cover plate 5-102, Fig. 304, be careful that the 
three springs are in their proper places, that slide-bar 5-125 
is seated in its groove and that none of the parts bind, due 
to pressure of the cover plate. The freeness of the pawls 
may be tested by pressing the finger on the magnet arma¬ 
tures, noticing whether or not they move easily and travel 
their normal distance, or until the armature is stopped by 
the adjusting screw. 

The following spare parts should be carried for the Auto¬ 
matic control units : (See page 869.) 

Two sets motor brushes. 

Two negative feed magnet springs, 5-149. 

Two spring coupling, 5-105. 


794 


HANDBOOK OF PROJECTION FOR 


The Spotlight 

T HE projectionist is sometimes called upon to operate 
a spotlight, and if without experience may feel 
nervous about making the attempt. This is unneces¬ 
sary, as the apparatus is simple and easy to manipulate. It 
consists essentially of a lamphouse, similar to the ordinary 
motion picture projector lamphouse, in which is an ordinary 
arc lamp similar to the arc lamp used for projecting motion 
pictures. There is an arrangement by means of which the 
lamp may be quickly advanced or pulled back in order to 
alter the distance of the crater from the lens, since it is this 
act which alters the size of the “spot,” or changes it to a 
“flood.” In the front of the lamphouse a single plano-convex 
lens is mounted. There are no other lenses in connection 
with a “spot,” as such devices are called. The lamphouse is 
mounted on an upright, which is adjustable in length, so that 
the height of the lamphouse from the floor may be changed 
at will. The upright is supported by a suitable base. On 
some of the smaller spots a small wire coil rheostat is 
mounted, but with most modern spots the rheostat is a sep¬ 
arate unit. 

The lamphouse is so mounted that it may be swung from 
side to side, or tilted up or down, since by these movements 
the direction of the light beam is directed. 

Roughly this decsribes the old type “spot,” which same is 
illustrated in Fig. 307. In Fig. 306 we have a view of the 
optic end of it. 

The lens usually is six inches in diameter for small spots, 
though larger ones may have lenses eight inches in diameter. 
There is a single plano-convex lens only. 

As said before the size of the “spot” is controled by the 
distance of the crater to the lens. The further away it is the 
smaller the “spot,” and the closer it is the larger the “spot.” 
If it be shoved close enough to the lens a “flood” will result, 
which may be made to cover the entire stage. 

Spot lights use anywhere from fifteen to fifty or more 
amperes D. C., which is taken through an ordinary rheostat 
of suitable capacity. 

HANDLING A SPOT. —No especial skill is required to 
handle a “spot.” A man of ordinary intelligence should, after 


MANAGERS AND PROJECTIONISTS 


795 


a few moments practice, be able to cover an actor when 
moving about, and do it well, too. The difficulty is not in 
handling the device, but in the matter of carbon setting. 
With the old style arc lamp considerable experience and skill 
is necessary to get an approximately round spot which is 
free from ghost. The spot is nothing more or less than an 
out-of-focus photograph of the crater of the positive carbon, 
therefore, unless the crater presents a round surface or cir¬ 
cumference to the lens, the resultant spot will not itself be 
round; also faulty carbon setting is likely to produce a ghost 
in the spot. 

The lamp should be given a pretty heavy angle, and the 
carbons should be set much the same as for motion picture 
projection. It is then up to the projectionist to experiment 
with the amount of advancement of the lower carbon tip 



with relation to the other, and with the angle of the lamp 
itself, until he gets the condition which produces the most 
nearly round spot, and one free from ghost. 

KIND OF CARBONS. —It will, of course, be necessary to 
use a cored carbon for positive. Any good projection car¬ 
bon will do. For negative the projectionist may try a cored 
carbon, of smaller diameter than the positive, and a Silver 
Tip and Hold Ark, using the one giving best results. 

Remember that following an actor with a spot is childishly 
simple. The hard job is to get and keep a clear, round spot. 

The spotlight port in the wall should be 16 to 18 inches in 
diameter, round or square, as preferred. A color wheel suit¬ 
able for mounting on a spot may be had from any supply 
dealer. It is a very necessary adjunct to a spot light. Color 
slides may also be had. 

A. C. SPOT. —We do not advise you to try it, unless you 
use pretty high amperage. It is possible to get a spot with 




796 


HANDBOOK OF PROJECTION FOR 


A. C. at ordinary amperage, but it will not be a good one. 
Seventy-five amperes is what we would consider as the mini¬ 
mum amperage for a spot light, if good results are to be 
had. 

HIGH INTENSITY SPOT.— The Nicholas Power Company 
is marketing a spot which uses the high intensity lamp. This 
spot is, in many respects, a distinct innovation. 

The base is heavy and has three extensions or “feet,” one 
of which is about four inches longer than the others. The 
long leg goes toward the back of the lamphouse. The lamp- 
house is 29 inches front to back, 31 inches from base to top 
of vent cone, and 11J4 inches wide. It is 
made of heavy material, with double-wall 
doors. Adapters are provided, which 
enable the use of anything from a 4 to 
an 8-inch diameter lens. These adapters 
fit into a groove in casing A. In front of 
the lens, also fitting into a groove in cas¬ 
ing A, is an iris diaphragm with an 8-inch 
opening, constructed entirely of brass. 
In front of the iris are two grooves, 
designed to carry either the support for 
a color wheel, or color slides. The 
observation window in the lamphouse is 
10 inches long by 3 inches wide, and is 
covered with dark red glass. Casing A 
is of grey cast iron. 

The construction is such that once the 
spot is in the desired location it may, if 
desired, be locked there by means of 
wheel B and handle C. By loosening 
wheel B the lamphouse may be swung 
clear around on the pedestal. Handle 
C is a locking device, so that the lamp- 
house may be tilted to any desired angle and locked there. 
With both handles B and C unlocked the spot may be moved 
to any desired location, from on the floor three feet in front 
of or back of the machine, to an angle of probably 75 degrees 
upward. 

The machine, exclusive of the pedestal, weighs probably 
150 pounds, yet so perfect is the construction and the balance 
that it may be moved in any direction with one finger; also, 
the balance is automatically maintained, regardless of the 
position of the lamp, because when the lamp is pulled back, 
weight D automatically moves forward just enough to coun- 



Figure 307. 



MANAGERS AND PROJECTIONISTS 


797 


terbalance the weight of the lamp. Handle E controls the 
forward and backward movement of the lamp and the 
weight. Rod F has teeth on its under side and rod G teeth 
on its upper side. Between these two rods is a toothed 
wheel. This wheel is actuated by rod F when the lamp 
moves forward or backward, and this, acting through the 
toothed wheel, moves rod G in the opposite direction, thus 



Figure 308. 

carrying weight D backward and forward to counterbalance 
the weight of the lamp, and thus keeps the lamphouse 
always evenly balanced on the pedestal. 

The spot marks a very great step forward in the produc¬ 
tion of high-class equipment for theatres. 

DATA CONCERNING SPOTLIGHT LENSES.— The Uni¬ 
versal Stage Lighting Company, better known as Kliegl 
Brothers, 321 West 50th street, New York City, from whom 

















798 


HANDBOOK OF PROJECTION FOR 


spotlight lenses of all sorts may be had, supplies the follow 
ing valuable data: 

“We are very often requested to supply a lens to give a 
small (5 foot) spot when the distance of projection is long 
It is not possible to handle such requests intelligently unless 
the following information accompany the order: (A) Dis¬ 

tance lens to stage; (B) diameter lens the spotlight will ac¬ 
commodate; (C) length of spotlight hood, or greatest distance 
crater can be gotten from face of lens. 

“Our regular 25-ampere stage spotlight, which uses either 
a 5 or 6 inch diameter lens, will give an excellent three (3) 
foot spot at any distance up to 40 feet. This spotlight can¬ 
not be used to give a five foot spot at 100 feet, because the 
hood is not long enough. In other words, it is impossible to 
get the crater far enough from the lens. 

“The following data will be of assistance to the projection¬ 
ist, or to the spotlight operator who may wish to obtain a five 
foot spot at various distances. You will note that some 
lenses give the same size spot at widely different distances, 
without altering distance of crater to lens. This is because 
at the outer end of the beam its diameter varies but little over 
a long distance. 

“NOTE.— Before ordering lenses it is of the utmost import¬ 
ance that you try your lamp and see if you can get the crater 
the required distance from face of lens. If you cannot, then 
you cannot get the results you want unless the length of 
hood be altered so that you can get greater distance between 
crater and lens. 

“To gain a five foot spot at longer distance you must be able 
to get the crater back a greater distance, but it must be con¬ 
sidered that the further the crater is from the lens the 
greater will be the waste of light—see page 162, hence when 
crater-to-lens distance is increased the amperage must also 
be increased if the brilliancy of the spot is maintained. For 
this reason our long distance spot lamps are equipped with 
a 35, 50, 70 and 100 ampere rheostat.” 

IMPORTANT.—It is essential that proper carbons be used. 

If this be not done there will most likely be shadows, rings 
and lack of brilliancy in the spot. It is not sufficient—in fact 
it will not do for the projectionist or spotlight operator to 
place a pair of ordinary ^ths cored carbons in the lamp. 
With direct current, cored projection carbons must be used 
for upper and solid “Silver Tip” carbons for lower. When 
using A. C. use cored white flame carbons. 


MANAGERS AND PROJECTIONISTS 


799 


To obtain approximately a five (5) foot diameter spot. 

Distance crater 


Distance 



must be from face 

lens 

Diameter 

Focal 

of lens to obtain 

lo stage 

of lens 

length of lens 

5 ft. diameter spot 

75 feet 

5 inches 

9 inches 

7 inches 

100 feet 

5 inches 

9 inches 

8% inches 

75 feet 

6 inches 

12 inches 

WV\ inches 

100 feet 

6 inches 

12 inches 

11J4 inches 

150 feet 

6 inches 

12 inches 

\\y 4 inches 

75 feet 

6 inches 

13 inches 

12" for 4' spot 

100 feet 

6 inches 

13 inches 

12" for 4' spot 

125 feet 

6 inches 

13 inches 

12" for 4' spot 

150 feet 

6 inches 

13 inches 

12J4" for 4' spot 

75 feet 

8 inches 

13 inches 

12J4 inches 

100 feet 

8 inches 

13 inches 

1254 inches 

125 feet 

8 inches 

13 inches 

12y inches 

150 feet 

8 inches 

17 inches 

\2 l / 2 inches 


IT TAKES LESS TIME TO 
DO A THING RIGHT THAN 
TO EXPLAIN WHY YOU 
DID IT WRONG 



800 


HANDBOOK OF PROJECTION FOR 


Stereopticon 

E VERY projection room should be equipped with a 
stereopticon, though a dissolving stereopticon is no 
longer necessary in most moving picture theatres. 

In the early days of the business the almost universal 
custom was to project stereopticon slides designed to “illus¬ 
trate” the words of a song sung, at the same time, by a 
singer. This practice has almost entirely ceased, and with 
its passing the need for a dissolving stereopticon has also 
very largely ceased. A small, single stereopticon is all that 
is ordinarily necessary in the modern projection room. 

Many exhibitors do not provide even this, utilizing instead 
a motion picture projector stereopticon attachment. This 
of course can be done, but there are serious objections to the 
plan, one being that the condenser suitable for the projection 
of motion pictures under a given condition, is very seldom 
suitable for the projection of slides when the projection 
distance is the same, and the height of the “still” is limited 
to the height of the moving picture because the latter is 
bordered in black, and even though it be only advertising 
slides that are projected, the job ought nevertheless to be 
done in the best possible manner. See “Combination Pro¬ 
jector,” Page 802. 

The single stereopticon consists of a lamphouse and lamp, 
a condenser, a slide carrier and a projection lens. The as¬ 
semblage may be had with or without a supporting stand. 

SLIDE SIZE. —Slides used in the United States and Can¬ 
ada measure 3.25 inches by 4 inches over all. The actual 
opening in the mat, or the size of the picture as outlined by 
the paper mask, is presumed to be two and three-quarters 
inches by three inches, though in practice the size of mat 
openings vary widely from this measurement. 

Due partly to the fact that the revolving shutter of the 
moving picture projector cuts about fifty per cent, of the 
light, and in part to the fact that a still greater percentage 
of the total light is wasted at the spot, whereas with the 
stereopticon the entire beam of light from the condenser is 
available at the screen, less only the relatively small percent¬ 
age lost in the projection lens itself, stereopticon pictures 


MANAGERS AND PROJECTIONISTS 


801 


may be projected with a very much less brilliant light 
source than is necessary with motion pictures. With a prop¬ 
erly selected optical system the stereopticon will project a 
very excellent picture sixteen to eighteen feet wide with 15 
amperes D. C. As a matter of fact high amperage for 
stereopticon projection is objectionable, because the resultant 
heat may and probably will crack the slide if it be left in 
the light for more than a very brief period of time. 

This is another reason why a stereopticon should be in¬ 
stalled in the projection room if any slides at all are to be 
projected. If the theatre projects slides advertising future 
programs they miss their purpose unless left on the 
screen a sufficient time to be read by the audience, and this 
can hardly be done when they are placed right up against a 
hot condenser through which the light from the 50 to 100 
ampere crater is passing. Then, too, where a Mazda light 
source and a prismatic condenser is used for moving picture 
projection, slides cannot be projected with it at all. 

GAS LIGHT. —So little light is necessary for the proper 
projection of stereopticon pictures that it is possible to get 
excellent results by the use of ozo-carbi, lime-light, or even 
by the use of acetylene gas. 

WHY CRACKED CONDENSERS SHOW.— Many ama¬ 
teur projectionists are puzzled by the fact that whereas a 
crack in one of the condenser lenses will not show on the 
screen when projecting moving pictures, it shows very plainly 
when projecting still pictures. 

The answer is simple. In the stereopticon the slide and 
the screen represent the two conjugate foci points of the 
projection lens, therefore it is the slide that is focused at 
the screen, and since the condenser is right up against the 
slide, any imperfection therein will also be more or less 
sharply focused at the screen. It therefore follows that a 
crack will show, and, if it be in the converging lens will show 
very sharply, because the face of the converging lens is 
practically at the conjugate foci point. On the other hand, 
with the moving picture projector, since it is the screen and 
the film that are the conjugate foci points of the projection 
lens, and the condenser is removed from the conjugate foci 
point (film) by many inches, any imperfection therein will 
not be focused at the screen, therefore an imperfection such 
as a crack in the condenser will not show, even though it be 
a very bad one. 

SLIDE CARRIER LIGHT LOSS.— If the optical system of 


802 


HANDBOOK OF PROJECTION FOR 


a moving picture projector be such that the projection lens 
will pick up the entire beam from the full diameter of the 
condenser (about 4.25 inches), then the placing of a slide 
carrier permanently before the condenser lens will operate 
to cut down the illumination at the screen, and cut it down 
very considerably, too. See Fig. 42 A, Page 177. If, on the 
other hand, the condition be such that the projection lens is 
unable to pick up the beam from a condensing lens more 
than three inches in diameter, then the slide carrier will 
cause no loss. As a general proposition, however, we would 
very strongly advise against the permanent location of a 
slide carrier in front of the condensing lens of a moving 
picture projector. Under some conditions it does no harm, 
but under other conditions it will cause a very great loss of 
light, and one can never tell whether or not the man in 
charge of any particular projector will be able to determine 
whether the carrier is doing damage or not, hence, the 
safest way is to avoid the installation of a carrier in front of 
the lens. 

COMBINATION PROJECTOR.— Whereas we strongly ad 
vise against using the moving picture projector stereopticon 
attachment, still we realize that it is being done in many 
cases, and probably will be for some time to come. If the at¬ 
tempt is made to project slides with the current used to 
project moving pictures there will probably be a great num¬ 
ber of them broken. This cannot be entirely avoided if a 
projector be used for slide work immediately after moving 
pictures have been projected, because the condenser will in 
that case be very hot, and the heat stored therein will break 
the slides if they be left in the carrier for more than a few 
seconds. Slide breakage may be avoided, however, by using 
the projector which has been standing idle, and reducing the 
current. If A. C. is used at the arc, and current is taken 
through an economizer, the current reduction is merely a mat¬ 
ter of tuning the adjustment lever to low. If rheostats are 
used, the matter may be taken care of either by installing a 
rheostat of suitable capacity in a shunt circuit, as shown at A, 
Fig. 309, or by second rheostat in a shunt circuit, as shown 
at B, Fig. 309, so that when the switch is closed the resistance 
rheostat D is eliminated, but when the switch is open the two 
rheostats are in series, which will reduce the current to any 
desired number of amperes, the amount of reduction depend- 
on the amount of additional resistance offered by rheostat D. 

If a motor generator set is used the amperage may be re- 


MANAGERS AND PROJECTIONISTS 


803 


duced by means of the field rheostat when slides are to be 
projected. It is also quite possible to so arrange a rheostat 
that it may be cut into series with the generator of a motor 
generator and the arc, as per the shunt circuit at A in Fig. 
309; in which case there would, of course, be no rheostat 
B, the shunt being merely connected around the switch. 

With a mercury arc rectifier of modern type it is possible 
to reduce the amperage for slide projection merely by moving 
the dial switch to “low.” 

No matter what apparatus you have for supplying current 
you can arrange to reduce current for slide projection if 
you know your business, always provided the exhibitor will 
provide what, if anything, is needed to do it. 

THE DISSOLVER. —The dissolving stereopticon consists 
of what amounts to two separate, single stereopticons, 


S.P.'LTSWITZH 

u — 


3 


A 


A 





Figure 309. 

mounted on one base, usually one above the other, with an 
arrangement either in front of or attached to the projection 
lenses, by means of which the closing of one lens automatically 
opens’the other, or vice versa, the opening of the one lens 
being in exact proportion to the closing of the other, so that, 
for instance, when one lens is half open, the other auto¬ 
matically is half closed, and when one is entirely closed the 
other is wide open. This latter is known as the dissolving 
shutter.” 

The reason it is called “dissolving” is as follows: Supposing 
one lens tc be wide open and a picture being projected through 
it to the screen. We start to open the other lens by moving 






















804 


HANDBOOK OF PROJECTION FOR 


the handle of the dissolver, which at the same time starts 
to close the open lens, so that a second picture is projected 
through the opening lens with constantly increasing brilliancy, 
as the brilliancy of the picture already on the screen is gradu¬ 
ally diminished by the closing of its lens. The opening and 
closing is in exact proportion, so that at the time both lenses 
are exactly half open there are actually two pictures on the 
screen, each of exactly equal brilliancy, the total effect being 
that the second picture is “dissolved” into the first, or the 
first is “dissolved out” by the second. 

There are two advantages in the dissolver as against the 
single stereopticon. First, the dissolving out of one picture 
by the other is a much more pleasing effect than can possibly 
be had with a single stereopticon. Second, when using a 
single stereopticon, unless the projectionist is very careful 



fi/f.R 


Figure 310. 


while removing or' inserting slides, he will move the carrier, 
which will cause the picture on the screen to move or jump. 
This is not possible with the dissolver. 

It is, however, hardly worth while to go to the expense of 
a dissolver if only advertising slides are to be projected. The 
careful, painstaking projectionist can avoid movement of the 
picture on the screen while inserting the second slide, and by 
the use of an Ingento Slide Carrier not only is movement of 
the picture on the screen avoided, but the change of pic¬ 
tures on the screen is made very rapidly, and with a semi¬ 
dissolving effect, therefore 

Where advertising slides only are to be projected, we would 
recommend a small, single stereopticon, equipped with an In¬ 
gento dissolver, which latter may be had of any good supply 
dealer. Such a stereopticon may be equipped either with 












































MANAGERS AND PROJECTIONISTS 805 

Mazda or arc lamp light source, but Mazda will serve every 
purpose, and serve it well. 

In Fig. 310 the electrical circuits of a dissolver is illustrated. 
A is the projection room switch board, B-B the fuses for 
each circuit, C-C, the dissolver table switch for each circuit, 
D-D the two rheostats, one of them for each circuit. A 
dissolving stereopticon requires two complete circuits—just as 
complete as though each were the circuit of a single stereop¬ 
ticon, which it, in fact, is. Rheostats should not exceed 20 
amperes D. C. capacity, and if properly handled, 15 amperes 
D. C. will be plenty, provided the optical system be what it 
should be. If the light source be an A. C. arc, then a con¬ 
siderably higher amperage will be necessary—say 30, 35 or 
even 40. 

Where a dissolver takes current through a single econo¬ 
mizer it is possible to connect as per Fig. 311, though it re¬ 



quires considerable practice to handle the arcs, and unless 
handled skillfully they will go out. In Fig. 311, A is the 
economizer and B a D. T. S. P. knife-switch of suitable ca¬ 
pacity. With the switch in position as shown, the two lamps 
are in series. To start the arcs it is necessary to freeze the 
carbons of one lamp, and then strike the arc of the other, 
after which the carbons of the second lamp may be separated, 
and the second arc thus formed. 

This can be, and has been done, but as we have said, it is 
difficult to handle the arcs, and unless one has considerable 
practice there may be times when the picture on the screen 
will suddenly vanish. 

The same thing can be done with rheostats, but rheostats 
are so low in cost that there would be no real necessity for 
attempting so difficult a thing. 

DISSOLVING SHUTTER.— The best dissolving shutter 
consists of an iris diaphragm affixed to each projection lens, 






















806 


HANDBOOK OF PROJECTION FOR 


the two so connected that the closing of one opens the other, 
or vice versa. However, anything that opens one lens in 
proportion as the other is closed accomplishes essentially the 
same effect, and it is entirely practical for the projectionist 
himself to make a dissolving shutter which will work nearly 
as well, insofar as screen results be concerned, as the iris 
diaphragm. This is illustrated in Fig. 312, in which diagram A 
and diagram B show two different ways of doing it. In A, 
two metal shutters, with saw-tooth edges, are attached to 
an iron bar of proper length, the same being mounted on a 
bolt X which is attached to the projection room wall, and op¬ 
erated by handle Y. The only thing to be sure of is that the 
shutter be so made and placed that when one lens is exactly 

half open the other is 
half closed. 

At B the same thing 
i s accomplished b y 
means of a board, cut 
as shown. Instead of 
rocking sidewise this 
board raises straight up 
and down. The bolt by 
means of which it is 
held is, as in the case of 
A, attached to the pro¬ 
jection room wall. Tn 
the latter case there 
must be either a 
counter weight on 
the handle, or some kind of a friction device on the sustaining 
bolt, which will prevent the shutter dropping down by its own 
weight. 

PROJECTOR STEREOPTICON DISSOLVING.— It is quite 

possible to arrange a dissolving effect where the projection¬ 
ist has two moving picture projectors, each equipped with a 
stereopticon attachment. We do not advise this, but it can be 
done. It is only necessary to arrange a shutter somewhat 
similar to A, Fig. 312, but with the blades sliding up and down 
in grooves in front of the lenses, instead of being attached 
to a bar, the blades being connected by a cord passing 
through pulleys on the ceiling, so that raising one lowers the 
other, or two iris diaphragms may be used, the same being 
connected by means of a light chain or cord running through 
















MANAGERS AND PROJECTIONISTS 807 

pulleys on the ceiling, so that the opening of one closes the 
other. 

Such an arrangement is awkward, because of necessity for 
reducing the current of both projection arcs, and because the 
projectionists must stand between the projectors and reach 
over to put the slides in the right hand carrier. We repeat, 
we do not advise it, but it can be done. 

MATCHED LENSES. —The lenses of a dissolver must be 
so matched that each will project a picture exactly the same 
size. When ordering lenses for a dissolver the fact that they are 
for that use should be made clear and the dealer instructed 
to send matched lenses. 

LENSES IN REGISTER. —It is necessary that the lenses of 
a dissolving stereopticon be so set that they will “register” 
accurately. By this it is meant that the light projected by 
each of them will occupy exactly the same space on the 
screen.. 

There are several ways of testing the register of the lenses, 
but the following will suffice. Select any stereopticon slide, 
place it in the carrier, the lower one if it is a regular dissolv¬ 
ing stereopticon, and so adjust the lens that the picture reg¬ 
isters where you want it on the screen. Either make a small 
mark on the screen at the two lower corners of the picture, 
or if it cannot be reached, then lean something against the 
screen so that its upper end will just touch the lower edge of 
the picture at one of the corners. Next place the same slide 
in the other carrier and adjust that lens until it registers in 
the same place. The important part of this is that the same 
slide be used in both carriers, because if different slides are 
used there might be a difference in size of opening in the mat. 

For accurate registering the better way is to proceed as 
follows: Make two slides of tin or thin sheet metal, so that 
they will fit snugly in the carrier. Laying one over the other 
so that they accurately register with each other, punch a 
small hole near to and equidistant from each edge of the 
slide. Driving a shingle nail through will do. With an ordi 1 
nary slide, so adjust the lower lens that the picture is where 
you want it on the screen, and so adjust the slide carrier that 
the picture on the screen is level, then place the metal slides 
in the carriers, being sure that matched holes are on the same 
side, and adjust upper lens and carrier so that the holes match 
on the screen. 

HAVE PICTURE LEVEL. —It is essential that the carrier 
be so adjusted that the picture is level on the screen. This 


808 


HANDBOOK OF PROJECTION FOR 


may be accomplished by raising one side of the carrier, block¬ 
ing it up with some non-inflammable substance, first being 
sure that the dissolver, as a whole, sets perfectly level. 

THE PICTURE. —Supplied with proper equipment, there is 
ordinarily no excuse for anything except perfect stereopticon 
projection. Yellow corners in the stereopticon picture, or 
a ghost in its center, are positive evidence of one of two 
things, viz.: the condensing system is not right, or the pro¬ 
jectionist has not properly adjusted his light or his optical 
train. 

THE REASON. —The stereopticon projection lens necessary 
to project a picture the same width as a moving picture at 
the same distance is of much longer E. F. than the M. P. pro¬ 
jection lens is because the aperture of the slide (opening in 
mat) is very much larger, hence not nearly so much magni¬ 
fication is required, and the shorter E. F. of a lens the greater 
the magnification to a given distance. 

THE PICTURE. —The stereopticon picture should not be 
too' brilliant, and should present a clean, clear, sharp-cut 
appearance. Its size should of course be according to the 
size of the auditorium, but when used in conjunction with 
a motion picture entertainment, there is no necessity for a 
stereopticon picture which will have greater height than the 
motion picture. If the screen is bordered in black, or any 
other color for that matter, it is of course impractical to 
have a stereopticon picture the same width as the moving 
picture, because the proportions of the slide mat and the 
motion picture projector are different. 

It seems to us that, as a matter of plain common sense, 
the standard slide mat opening proportions should be 
changed to match the proportions of the motion picture 
aperture, which would be a trifle less than 3x2.25 inches. 
This latter is the standard approved by the Society of Mo¬ 
tion Picture Engineers, which should be accepted by slide 
makers and put into general use immediately. 

DISSOLVING SLIDE CARRIER.— There is a slide car¬ 
rier, made by Burke and James, Chicago, called the “In- 
gento,” designed for use with a single stereopticon, which 
produces what its manufacturers claim to be a dissolving 
effect. This claim is not, however, strictly true, though the 
change of slides is made very quickly—so quickly that a 
fairly near approach is had to the dissolving effect. We can 
recommend this carrier for use with a single stereopticon. 
Its use with a dissolver presents no advantage whatever, 


MANAGERS AND PROJECTIONISTS 


809 


STEREOPTICON SLIDES. —Stereopticon slides consist of 
two pieces of very thin glass, each 3% inches by 4 inches, 
bound together with gummed paper binder strip. Between 
these glasses is a paper mask, known as the “mat,” which 
serves to outline the photograph, limiting the area through 
which the light can pass. 

The opening in the standard mat is 2J4 inches high, by 3 
inches wide. Mat openings, however, vary in size, and in 
the shape of the opening, the one we have given the dimen¬ 
sions of (2^x3 inches) being the standard usually used for 
advertising and song slides. See comments under “The Pic¬ 
ture,” page 808. 

The photograph may or may not be colored. If it is, water 
colors are used, which 
are applied by hand 
process. The second 
piece of glass is merely 
a clear piece of glass, 
called a “cover glass,’ 
the only function of 
which is to protect the 
photograph. 

The side of the glass 
bearing the photograph 
should always be to¬ 
wards the light, since 
otherwise everything 
will be reversed, and 
any written or printed 
matter contained on 
the slide will read 
backwards. Usually the mat bears printing, or some 

ornamental design. In placing the mat in the slide, 
the printed or ornamental side of the mat should be 
away from the photograph, then if this side of the mat be 
always placed next the light there will be no possibility of 
having reading matter reversed, though this does not guard 
against getting the slide in wrong side up. 

Slides are placed in the carrier bottom side up. If they 
are placed in right side up, the picture on the screen will 
be wrong side up. 

Fig. 313 illustrates the mat side of a slide—the side which 
goes toward the light. In the lower left-hand corner is a 
black spot. This is known as the “thumb mark.” It should 
always be in the lower left-hand corner as you hold the 



Figure 313. 






810 


HANDBOOK OF PROJECTION FOR 


slide right side up, in the position as shown in Fig. 313. 
When placed in the carrier, this mark will be in the upper 
right-hand corner as you look towards the screen. With 
the mat in the right way, and the slides properly marked, as 
indicated in Fig. 313 (thumb mark in lower left-hand corner), 
there can be no excuse for getting a slide in the carrier 
wrong. 

HANDLING SLIDES. —The projectionist who uses stere- 
opticon slides should be very sure they are perfectly clean 
before he projects them. Every bit of dirt on the face of 
the slide will show on the screen, and we know of no one 
thing which so thoroughly advertises a sloppy, careless, 
slovenly workman as- the imprint of his dirty fingers pro¬ 
jected to the screen because they are carried on the face of 
a slide he was too lazy or to careless to clean. 

Slides may be cleaned by breathing on them when cold, 
polishing quickly afterwards with a clean cloth, or by wash¬ 
ing with a mixture of half and half water and denatured alco¬ 
hol, polishing quickly afterwards. 

In removing slides from the carrier, the average projection¬ 
ist leaves the marks of his fingers thereon. This is because 
he does not handle them right. In placing a slide in the car¬ 
rier it should be handled by its thumb mark corner only. In 
taking it out it should be raised slightly with the middle finger 
and then seized between the thumb and forefinger and re¬ 
moved as per Fig. 314. Handled this way there will be no 
finger marks on the slides. 

CAUTION. —When using a single stereopticon, be very 
careful to ease the slide down into the carrier gently, so 
as not to cause the carrier to move. If the carrier moves, 
the picture on the screen will move. A rather ridiculous 
effect is produced when an audience is watching, for in¬ 
stance, a battleship, and due to the carelessness of the pro¬ 
jectionist in placing the other slide in the carrier, the whole 
ship, ocean and all, jumps up in the air a couple of feet and 
settles back with a bump. 

REPAIRING SLIDES. —In event a slide is broken, it may 
be made as good as new if the crack be in the cover glass 
only. In the event it is only necessary to remove the broken 
cover glass, substituting a new one, which has first been 
thoroughly cleaned, rebinding the slide as it was before. 
Gummed binder strip and cover glass may be obtained from 
any supply dealer. If, however, the crack is in the glass 
bearing the photograph, then the damage cannot be re- 


MANAGERS AND PROJECTIONISTS 


811 


paired. Where stereopticon slides are used, it is well 
that a few cover glass mats and some gummed binder strip 
be kept on hand in the projection room. 

MAKING ADVERTISING SLIDES.— It is entirely prac¬ 
tical to make slides designed to convey messages to the 
audience. There are many ways of doing this, some very 
simple and some rather complicated. The highest grade 
slides of this character are, of course, made by photography, 
and the most satisfactory results may be had by photograph¬ 
ing white lettering on black cardboard. The cardboard may 
be any size desired, from 6^4 inches high by 8 inches wide up 
to 2 feet wide. Any desired photograph may be attached to 
the card and surrounded with lettering. The white paint is 
made of dry white lead and thin glue, enough lead being 
used so that it is thick enough to cover well and not run. 
Being supplied with the advertising text matter, any com¬ 
petent sign painter can make the card, or with practice some 
one around the theatre may learn to do it very well, par¬ 
ticularly if he obtains books of architect’s alphabets to use 
as guides. The cards should be painted in the proportions of 
inches by 4 inches—that is to say, the cards may be any 



Figure 314. 







812 


HANDBOOK OF PROJECTION FOR 

size, but must be in those proportions. When finished the 
card is photographed in the usual way, and a positive print 
made on a slide plate, either by reduction, or by contact if 
the photograph is of slide size. 

CAUTION—In making the positive, remember that 
whereas the slide glass is 3 % inches by 4 inches, the mat 
opening is much smaller, and that the positive print must 
include all lettering within the area covered by the mat 
opening. 

If only one copy of a slide is needed it may be made by 
writing the desired matter on a white card, using black ink, 
and photographing the same. Before photographing, how¬ 
ever, reverse the plate in the lens holder and stop the lens 
down to make up for the focus being thrown out by the 
reversal of the slide. The plate will develop with white 
letters on a black background, and will be readily finished, 
the same as a contact slide from a negative. Unless you 
reverse the plate everything, including reading matter, will 
be reversed on the screen. 

It is also possible to write on perfectly clean cover glass 
by means of special inks, which may be had from supply 
dealers. It is also possible to write on transparent celluloid 
with India ink, and then print a photographic slide by con¬ 
tact. This latter method has the advantage of saving the 
expense of slide plate negative, and the celluloid, besides 
being low in cost, may be used over and over again, since the 
ink may be washed off. 

It should be remembered, too, that a black background 
slide with white letters is very much easier on the eyes of 
the audience than is the white background with black 
letters. 

When making photographic slides from celluloid, when 
the slide has been washed and fixed it should be set away 
to dry, and should not be moved during the drying process, 
since moving will cause unevenness of density. 

A fairly acceptable advertising, or other announcement 
slide, may be made by typewriting on light yellow or clear 
gelatine, being very careful, however, that you do not get 
your fingers on the gelatine, because if you do the marks 
will show. The gelatine should then be bound up between 
clean cover glass, using a mat. The typewriter ribbon must 
be well inked, and the type letters clean, for good results. 

Another way is to write on clean cover glass with special 
slide inks, which may be had from dealers. Another and 


MANAGERS AND PROJECTIONISTS 


813 


very excellent way is to dissolve dry gum demar in turpen¬ 
tine, allowing it to stand until it settles. The correct pro¬ 
portion, by measurement, is one of dry demar to twenty of 
turpentine. The solution is very thin, but it does the trick. 
First clean the cover glass thoroughly, then hold it per¬ 
fectly level and pour on some of the solution, allowing it to 
spread over the entire surface, after which the surplus may 
be drained back into the bottle from one of the corners, and 
coating allowed to dry. Glass thus treated may be written 
on with an ordinary pen and ink, just as one would write on 
paper. The drying process will require several hours, but 
the writing may be washed off with turpentine and the 
coating used many times. It is difficult to tell which is the 
coated side, therefore a permanent mark should be made on 
that side, or a small 
gummed sticker should 
b e affixed to one 
corner. 

Gelatine may also be 
used for coating, the 
process being the same 
as above, substituting 
for the demar coating 
one made by dissolv¬ 
ing clear gelatine in hot 
water. The gelatine 
may be had from any 
grocery or drug store; 
the proportion is one 
measure of gelatine to 
ten of water. The coat¬ 
ing is fairly satisfactory, but can only be used once. The 
solution should be passed through a very fine cloth before 
using. 

The projectionist who has occasion to make written slides 
will find the following to be a great help. Get a board, 
either of basswood or clear, soft pine, about 12 inches square. 
On one surface paste a sheet of paper 6 by 8 inches square, 
and on this paper paste an ordinary slide mat, laying off 
the paper surface inside the mat checker-board fashion, with 
the lines about 3/16 of an inch apart both ways, as per 
Fig. 315. Lay the glass you purpose to write on over the 
slide mat, and on two sides tack strips of cardboard to help 
you hold it in place. The lines will then serve as a guide 
for your writing, enabling you to do a neat job. 


































814 


HANDBOOK OF PROJECTION FOR 


Clean glass over which the tongue has been passed may 
be written on with ordinary ink after the saliva deposit has 
dried. 

Another very satisfactory way is to coat cover glass with 
an opaque coating, such as may be made by thinning coach 
painter’s black with turpentine, coating the glass and allow¬ 
ing it to dry, after which writing on the glass, using a sharp 
instrument, will produce clear letters with a perfectly opaque 
background. Coating cover glass with a solution of Bon Ami 
which may be had at any grocery store, and allowing it to 
dry, produces a similar result. The surface may be written 
on by using a sharp instrument- 

In fact we could fill pages of the various methods of 
making advertising slides, but what has been said is, we 
believe, sufficient. 


MANAGERS AND PROJECTIONISTS 


815 


Mazda Lamp Projection 

P ROJECTION by means of an incandescent light source is 
no longer an experiment. Its practicability, within cer¬ 
tain limits, has been very thoroughly established. Mazda 
lamp projection now is, and for a considerable time has been 
giving perfect satisfaction in a very large number of theatres. 

In order to intelligently decide as to the advisability of 
substituting Mazda lamps for the arc lamp, it is necessary 
that the exhibitor and the projectionist have a good funda¬ 
mental knowledge of the various things involved. 

SOURCE BRIGHTNESS AND UTILIZATION OF LIGHT. 
—Let us first consider the possibilities of the two sources of 
light, from the view point of brilliancy per unit area, and the 
area of the light source itself. 

The crater of the electric arc is the most brilliant source 
of artificial light evolved up to this time. This is because 
the floor of the crater of the electric arc is and must be 
raised to the temperature necessary to volatilize, or vaporize 
carbon, which is the hardest, most refractory substance 
known to science. The brilliancy per unit area of the ordinary 
projection arc crater (cored carbon) is between 132 and 160 
candle power per square millimeter. What the brilliancy 
of the high intensity arc crater per unit of area is we do 
not yet know. 

The Mazda light source cannot possibly equal the brilliancy 
per unit area of the electric crater, since the temperature 
necessary to produce such a result would instantly volatilize 
the lamp filament, and thus destroy the light source. In the 
Mazda lamp we therefore must be content with a light source 
much less brilliant, per unit area, than is the crater floor of 
the electric arc, but this is overcome to some extent by being 
able to locate it much nearer the lens. 

Due to the relatively high brilliancy per unit area of the 
electric crater, it is not to be hoped that the Mazda lamp can 
or ever will furnish a screen illumination equal in brilliancy 
to that supplied by the high intensity electric arc. Just how 
nearly the Mazda lamp will be able to duplicate the perform¬ 
ance of the arc is, however, a matter for future decision. 
The problem of determining the possibilities with the Mazda 


816 


HANDBOOK OF PROJECTION FOR 


lamp for motion picture projection purposes involves many 
things. First of all, there is the possibility that the condenser 
can be and will be supplanted by an ellipsoid reflector, or 
other means of condensing the light, or of utilizing the light 
from a source of larger area, which will very greatly increase 
the possible screen illumination supplied by a Mazda light 
source. When working with a condenser lens, however, the 
thing becomes very complicated. The principal reason for 

this is that the area of a light 
source is limited so far as 
present procedure goes, when 
that source must be projected 
through a small aperture by a 
condensing lens, and the beam 
again picked up by a second 
lens system (projection lens) 
beyond the aperture. 

Under conditions prevailing 
with the electric arc it has 
been impractical to use a light 
source of appreciably greater 
diameter than one half inch 
and the same limitation has 
thus far prevailed with the 
Mazda lamp, but with this 
difference: due to the differ¬ 
ence in heat, the Mada light 
source may be, and is placed 
very much nearer a condenser 
lens than can be the crater 
of an electric arc of equal 
area, therefore the condenser 
will pick up a very much 
greater percentage of the to¬ 
tal light (see Fig. 364, page 
162) when working with the Mazda lamp than when working 
with an electric arc. 

The use of a large projection lens diameter should, in 
theory, compel an increase in the width of the revolving 
shutter master-blade. That it does so may be disputed by 
some, because of the fact that many projectionists change 
from a small to a large diameter projection lens without any 
apparent necessity for altering the revolving shutter master- 
blade. This is true with the arc as well as with the Mazda 



Figure 316. 







MANAGERS AND PROJECTIONISTS 


817 


lamp, but it in no way alters the truth of the proposition that 
the larger diameter lens requires a wider master blade than 
the smaller diameter lens. It simply means that the projec¬ 
tionist was using an unnecessary width of master-blade while 
using the smaller diameter lens. In other words, while using 
the small diameter lens he was using a master-blade wide 
enough for a large diameter lens, hence was working unin- 
telligently and wastefully. 

The foregoing may not sound very impressive, but it never¬ 
theless is a fair statement of the main elements of the 
problems involved, when it comes to a comparison of the 
electric arc and the Mazda lamp as a motion picture projec¬ 
tion light source. 

Since the Mazda lamp filament is in fixed position, a glass 
mirror reflector, spherical 

| j-j ^♦-»-» 4 o r\ 1 a a/I K n V-» i /A « 4- 



Figure 318. 


Figure 317. 


which reflects through the spaces between the filament coils 
a large percentage of the light which would otherwise not 
reach the condenser, and hence would be wasted. 

THE MAZDA MOTION PICTURE PROJECTOR LAMP.— 

In Fig. 316 we see one of the latest Mazda motion picture 
projector lamps illustrated, and in Fig. 317 we see the filament 
thereof at exactly full size. A A, Fig. 316 are the supports 
for the filament, which supports are current carrying and of 
opposite polarity. 

The support of the filament has been one of the most 
serious problems encountered by Mazda lamp engineers. The 
reason this point has caused so much trouble and vexatious 
delay in the perfection of the Mazda projector lamp is that 






818 


HANDBOOK OF PROJECTION FOR 


the four coils must be held perfectly straight, so that as a 
whole, they present an even, flat surface to the collector lens. 
This seemingly simple thing proved to be an exceedingly 
difficult problem, because of the fact that the filament is 
subjected to very heavy expansion under the high tempera¬ 
ture at which it must operate, contracting to normal length 
again when it cools off. This alternate expansion and con¬ 
traction occurs frequently, every time the lamp is started or 
stopped, hence unless the coils be supported in precisely the 
right way they are likely to sag, warp or partially short-* 
circuit, as shown in Fig. 318. If this occurs it of course either 
entirely ruins the lamp or else very greatly impairs its 
efficiency, depending on how great the fault may be in the 
individual case. 

Mazda lamp engineers have finally, however, pretty well 

solved the problem, and a 
filament is now used which is 
of such composition and has 
such support that it is very 
dependable. True, an occa¬ 
sional coil still will fail, and 
probably always will, but 
they are few, and the lamps 
are guaranteed, within cer- 
ta in limits against such 
failure. 

HOW THE MAZDA 
LIGHT SOURCE IS MADE 

UP. —The Mazda motion pic¬ 
ture projector lamp light 
source is composed of four 
coils of tungsten wire. These 
coils are wound exactly the 
same as are ordinary coiT 
springs, or rheostat coils. 
Their exact size and length may be seen in Fig. 317. The 
base of the metal used is either a pure, or very nearly pure 
tungsten. 

As will be seen by examining Fig. 317, the coils are separ¬ 
ated from each other by a distance equal to a little less than 
their own diameter, and the four coils, as a whole, are so 
suspended and held that they present a perfectly flat surface 
to the face of the collector lens. 

From the foregoing it will be understood that the Mazda 



Figure 319. 




MANAGERS AND PROJECTIONISTS 819 

lamp is a light source, which does 
not, and cannot in itself present 
a solid, unbroken surface. Instead, 
it, of itself, presents the surface 
shown in Fig. 319. This fault is, 
however, in very great measure over¬ 
come by means of an image of the 
coils, which is reflected by a spherical 
mirror so placed (see Fig. 327) that 
it not only reflects, but also focuses 
an image of the coils between the 
coils themselves, as per Fig. 320. 
The image of the coils should be 
made the same size as the coils 
themselves, so that the image com¬ 
pletely fills the space between the 
coils, and overlaps on the coils very 
slightly. This for all practical pur¬ 
poses presents to the collector a solid, 
unbroken light source, and while it is 
true that the image of the coils is, 
both in theory and fact, somewhat 
less brilliant than the coils them¬ 
selves, still the difference is so slight 
that it is, to all intents and purposes, 
non-existent. 

SHORT CIRCUITING IN 
COILS. — Reverting, let us 
again examine Fig. 318, which 
shows a very bad case of 
filament distortion. It is an 
abnormal case, only shown to 
illustrate what Mazda engi¬ 
neers had to contend with in 
evolving a support for the 
lamp filament which would 
prevent this trouble. Such a 
case will probably never be 
found in the modern lamp. 

The dark spots in the fila¬ 
ment, Fig. 318, indicate short 
circuited turns of the coils, 
or, in other words, places 
where adjoining spirals of the 
coil touch each other, so that 



Figure 320. 



Figure 319^. 







820 


HANDBOOK OF PROJECTION FOR 


the current jumps across, instead of traveling around the 
spiral. This fault also is extremely unlikely to occur in the 
later type lamp, but it does sometimes happen, and a dark 
spot in a coil is evidence of such short-circuiting. 

It is, or should be, needless to tell you that in case a 
lamp filament does warp, distort or sag to any considerable 
extent the lamp should immediately be discarded, if for no 
other reason than because you can no longer focus the image 
of the coils entirely between the coils, which fault will result 
in a “streaky” screen. 



In Fig. 321 we have a chart provided by the G. E. Company, 
designed to show the action of the filament under expansion 
and contraction. The filament has very high resistance, there¬ 
fore when the current is turned on it heats up almost instan¬ 
taneously. This is graphically illustrated by curves in Fig 
321, in which the curve lines show the thermal expansion of 
the standard commercial filament, as now constructed. 

As you may see by examining Fig. 317, the filament is 
suspended from above. Further examination of Fig. 317 will 
show you that when heat is applied, any elongation of the 















































MANAGERS AND PROJECTIONISTS 


821 


filament, as a whole, must and will be downward, because the 
construction of its support is such that the coils are left 
free to expand downward, whereas the support from above is 
rigid. Not all the lower part of the support is shown in Fig. 
317, but it is shown very clearly in the drawing in Fig. 321. 
It consists of two long hooks which engage a wide loop in 
such way that the loop may slide up and down in the hooks. 

In Fig. 321 the horizontal row of figures represents time in 
minutes, and the vertical row represents expansion of the 
coils in fractions of an inch. The upper curve lines repre¬ 
sent expansion while filament is heating, and the lower lines 
contraction while the filament is cooling off. It is read thus. 
Suppose we draw a line straight up from 2 minutes in the 
horizontal row of figures, until it strikes the upper solid 
black line, and from there draw a horizontal line over to the 
vertical row of figures. We shall find it to strike the figure 
.015, therefore, since the solid black line represents the move¬ 
ment of the lower end of the filament under the influence of 
expansion, we see that at the end of two minutes after turning 
current on the cold filament, the lower end of the filament 
has moved .015 of an inch. The action of other points are 
read in the same way. You will observe that the total 
expansion and contraction reaches the surprising distance of 
almost .035 of an inch, but that this is not altogether in the 
filament itself, the actual filament expansion being repre¬ 
sented in the difference between lines A (solid black) and B, 
(broken line), the rest being in the supports. 

In reading the scale, the dotted line, the broken line and 
the solid line represent respectively the expansion and con¬ 
traction of the top of the supports, the top of the filament and 
the bottom of the filament. 

BLACKENING OF THE BULB.— As the age of a Mazda 
lamp increases, a deposit will form on the interior of the 
globe, which gradually causes a blackening of the glass. This 
is caused by what might be termed evaporation of the tung¬ 
sten filament. The principle reason for making the Mazda 
projector lamp globe tall is to provide room above the 
filament, as it has been found that this deposit will invariably 
be made on the upper part of the globe, hence 

With a tall globe the blackening of the glass is almost 
entirely above the plane of the filament. The blackening 


822 


HANDBOOK OF PROJECTION FOR 


which may occur at the plane of the filament is of such 
comparatively slight amount that it does not decrease the 
illumination of the lamp to any appreciable extent, if at all. 

The reason we say “if at all” is that, since the Mazda 
projector lamp is operated at constant current (amperage) 
instead of constant voltage, as is the case with the ordinary 
incandescent lamp, as the diameter of the filament is decreased 
by use, the lamp works at higher efficiency, hence gives off 
a sufficiently higher illumination to either entirely compensate 
for any blackening, or even more than compensate for it. 

The General Electric Company claims 
that, by actual tests during the life of a 
lamp, the total light flux of the lamp is 
increased by from two to five per cent., 
4 always provided the filament itself re¬ 
main in otherwise perfect condition— 
does not warp, distort or sag. If the 
filament be warped, then while the total 
light-giving power may not be affected, 
still the light delivered to the screen 
will inevitably be decreased because of 
the impossibility of focusing the fila¬ 
ment images between the coils, and thus 
securing an even, unbroken light source. 

A Mazda motion picture projector 
lamp should seldom be discarded 
because of blackening of the bulb. 
Usually the only reason justifying the 
discarding of a lamp which is still in 
working order is the bad warping, 
sagging or distortion of the filament, 
or other fault in the filament itself, 
such as short circuiting of some portion of the individual coils. 

QUALITY OF LIGHT. —There is a very decided difference 
in the tone of the light from the electric arc crater and from 
the Mazda lamp. Light from the electric crater is a clear, 
more or less bluish white, somewhat harsh and very brilliant 
light. Light from a Mazda lamp has, by comparison, a very 
much more mellow tone. To the ordinary eye it is, by con¬ 
trast, a yellowish white. This operates in two ways. The 
light from the arc is, by reason of its bluish whiteness, very 



Figure 322. 



MANAGERS AND PROJECTIONISTS 823 

penetrating. The bluish whiteness of the light has the effect, 
especially at high amperage, of causing the white in the 
screen image to appear more or less chalky and unnatural. 
This the light from the Mazda lamp does not do. It gives 
to the screen image a more natural appearance, and the 
more mellow tone of the light is more restful to the eye. 
This is, however, qualified by the fact that if the screen 
illumination be of too low intensity there may be eye-strain 
induced through difficulty in discerning detail in the image. 



Figure 323. 


In Fig. 323 we may see the reason for using a large diameter 
projection lens. A laboratory Mazda lamp set up is shown, 
using a prismatic condenser, such as we see in Fig. 322. The 
prismatic condenser compels a very short distance between 
condenser and aperture, with a correspondingly wide diver¬ 
gence of the light beam on the projection lens side of the 
projector aperture, as shown. The possibility for loss of 
light through this condition and a small diameter projection 
lens may be understood by examining Figs. 46 to 57, pages 
181 to 193. 

In Fig. 324 we have the same identical set-up as in Fig. 323, 
except that whereas a small diameter projection lens is used 





824 


HANDBOOK OF PROJECTION FOR 


in Fig. 323, a lens of large diameter is substituted in Fig. 324, 
which eliminates nearly all the light loss because the wider 
diameter enables the lens to pick up nearly the entire beam. 
The print (Fig. 324) shows no light loss at all, but the original 
photograph shows that even the large diameter lens fails 
to cover the entire beam, so that there is still quite a bit of 
loss. 

In Figs. 325 and 326 we have the same identical set-up, 
insofar as concerns distance of projection lens, but instead 
of the prismatic condenser there is the regulation 2-lens 
piano convex combination ordinarily employed where an arc 
light source is used. This, you will observe, because of the 



Figure 324. 


greater distance from condenser to aperture, enables the 
smaller projection lens to pick up nearly all the light. 

Again the print shows no loss, Fig. 325, but the original 
photograph did show some loss. The larger lens, Fig. 326, 
covers the entire beam. On the other hand, however, there 
is loss of light between the two condenser lenses and an 
additional reflection and absorption loss of about 12 per 
cent, in the added lens; also the light source is located a 
decidedly greater distance from the face of the collector 
lens than it is in the case of the prismatic lens. Exactly 
what the possibilities, in light loss and other things as be¬ 
tween the two systems may be we are unable to say. The 



MANAGERS AND PROJECTIONISTS 


825 


thing is altogether too complicated, and we could not under¬ 
take to advise you on that point. It is to be observed, how¬ 
ever, that there are a great many more installations of 
prismatic than of piano convex, which may or may not in¬ 
dicate superiority for the prismatic. 

RELATIVE LIGHT TRANSMITTING POWERS.— Tests 
made by the engineering department of the General Electric 
Company as to the light transmitting power of small and 
large diameter projection lenses, commercially known as 
No. 1 and No- 2 lenses, show that, working without a pro - 
jector revolving shutter the large diameter lens transmits 
double the light flux transmitted by the small diameter lens. 
This, however, only holds good where distance between con- 



Figure 325. 


denser and aperture is short, as where the prismatic con¬ 
denser is used. Both the prismatic and piano convex sys¬ 
tems have advocates, and both have advantages and dis¬ 
advantages. We do not care to take sides. The thing has 
too many complications. Examine the merits and demerits 
of the two systems for yourself. It is one matter on which 
we do not, at least as yet, care to offer advice. 

Remember this, however, if a prismatic condenser be used 
on a combination projector (M. P. projector with stereo 
attachment), it will be necessary to have a separate set of 
piano convex condensers for the stereopticon, which same 
may, however, be used for motion picture projection at any 
time, if it is so desired, 




826 


HANDBOOK OF PROJECTION FOR 


CONTROL APPARATUS. —The Mazda motion picture 
projector lamp filament must, in order to secure maximum 
screen illumination, be operated constantly at the full labeled 
capacity of the lamp. The instant the amperage drops below 
the labeled capacity of the lamp the screen illumination is 
decreased, and the decrease is very rapid. At 28 amperes, 
for instance, the screen illumination from a 30 ampere lamp 
drops to about 73 per cent, normal, and at 33 amperes it rises 
to about 160 per cent. 

From this the projectionist can see the vital importance of 
operating the lamp constantly at its maximum labeled amper¬ 
age of 30, carefully remembering, however, that while it is 
possible to operate it beyond its labeled capacity, and thus 



Figure 326. 

secure a very much higher screen illumination, it will very 
greatly shorten the life of the lamp. 

The amperage at the lamp should be under the control of 
the projectionist. Where the supply is A. C. this is accom¬ 
plished by means of a specially constructed transformer, 
known as the “Regulator.” These devices are made both 
automatic and for hand control. The automatic is opposed 
by many, on the ground that when the current is first turned 
on there is an instantaneous and rather heavy surge of 
current, which for the fraction of a second very heavily 
overloads the lamp filament. Further objection to the auto¬ 
matic is that when it is employed the projectionist has no 
control at all over the light producing power of the lamp. 




MANAGERS AND PROJECTIONISTS 


827 


With the hand controlled regulator the amperage at the 
lamp is entirely within the control of the projectionist. We 
recommend to you the hand regulator as best, except in 
cases where the current supply is subject to very heavy and 
constant fluctuations in voltage. 

Another advantage of the hand controlled regulator is 
that whereas with the automatic regulator the filament of 
the lamp is heated up at full load immediately, with the 
hand regulator it may be, should be, and by the careful pro¬ 
jectionist is brought up to maximum operating temperature 
gradually. The same reasoning applies to cooling the 
filament when shutting off the lamp. Still another advantage 



Figure 327. 


of the hand regulator is that it is small, compact and may be 
mounted on the projector, where it should be, whereas in 
general the automatic regulator is bulky, and not so well 
adapted for mounting on the projector. 

One of the most essential features in successful motion 
picture projection is the combining of regulator, lamphouse 
and ammeter into a single unit, placed on the projector, 
where it is right under the eye and hand of the projectionist. 

GENERAL ELECTRIC COMPANY REGULATORS.— The 

General Electric Company manufactures three forms of 
hand controlled regulators for Mazda lamps operating direct 
from A. C. lines. Each of these devices is mounted on the 
same base as the projector Mazda lamphouse. 







828 


HANDBOOK OF PROJECTION FOR 


The type HDS Form E, Figs- 327, 328, 329 and 329^4, hand 
controlled regulator is a straight transformer, wound and 
especially made for the regulation of amperage for the 30 
ampere, 900 watt Mazda C motion picture projector lamp, 
for supply voltages from 75 to 250 and frequencies from 25 
to 60. This type regulator has, according to manufacturer’s 
claim, an efficiency of 90 per cent. 

To Operate the regulator move lever K, Figs, 327, 328 and 
329 toward the lamphouse (clockwise) until pin M, Figs. 
328 and 329, strikes stop N, Fig. 328. With lever K in this 
position contact fingers H, Fig. 329, is on warming contact F, 
Figs. 329 and 329J4, which connects with coil D, Figs. 329 and 
329^4, through which the current must pass. Coil D is the 
warming reactance, or choke coil. It acts to prevent a 

sudden rush of current 
through the lamp fila¬ 
ment at the start, sup¬ 
plying, as it does, only 
sufficient current to 
bring the filament to a 
glow. 

If auxiliary lever L. 
Figs. 327, 328 and 329, be 
now shoved in, thus re¬ 
leasing stop pin M, and 
lever K be shoved fur¬ 
ther over toward the 
lamphouse, contact fin¬ 
gers H-H, Fig. 329 will 
successfully make contact with point G-G-G-G-G, Fig. 329, 
which has the effect of allowing more current to reach 
the lamp. 

Contact reactance C, Figs. 329 and 329^4, acts to prevent 
a momentary drop in illumination as the contact fingers 
move from one point to the next. 

To Shut off Current it is only necessary to move lever ’L 
backward, away from the lamphouse. This opens the circuit 
on the primary side of the transformer. 

In Fig. 329, A indicates the line leads and B the lamp leads. 
In other words you connect from contacts A to the line, and 
from contacts B to the lamp. 

Type HMC, Form B, hand controlled regulator, illus¬ 
trated in Figs. 330, 331 and 332, varies the amount of current 
supply to the lamp filament by magnetic action. It is made 



Figure 328. 





MANAGERS AND PROJECTIONISTS 


829 


for use with the 30 ampere, 900 watt Mazda motion picture 
projector lamp, and is designed for use on voltage from 100 
to 125 and 200 to 250 and on frequencies from 25 to 60. 

To Operate move the control lever L, Figs. 330 and 331, 
towards lamphouse until click of switch F, Figs. 331 and 332, 
is heard. Armature E, Fig. 331, then shunts the magnetic 
flux from secondary coil D, Figs. 331 and 332, so that only a 
small amount of current passes through the lamp filament. 
As lever L is moved further toward the lamphouse, armature 
E, Fig. 331, attached to lever L, and therefore rotating with 



Figure 329. 


it, increases the air gap and decreases the amount of shunted 
flux through it, the effect of this being to increase the cur¬ 
rent flow through the lamp filament. 

To shut off the current it is only necessary to move lever L 
away from the lamphouse, which rotates armature E until 
it trips pin G, Figs. 331 and 332, thus opening switch F, Figs. 
331 and 332, which will cause a clicking sound. 

In Figs. 331 and 332, A denotes location of line, and B of- 
lamp leads. 

Type HMC, Form A, hand controlled regulator, illustrated 
in Figs, 333, 334 and 335, varies the current strength mag- 






830 HANDBOOK OF PROJECTION FOR 

netically, and is designed for use with the 20 ampere, 600 
watt lamp. 

To Operate, turn on snap switch H, Figs. 333, 334 and 335, 
making sure that pointer on knob L, Figs. 333 and 334, is at 
the “low” position. Armature D, Fig. 334, will then be inside 
coil C, Figs. 334 and 335, and in this position it shunts the 
magnetic flux. As knob L, Figs. 333 and 334, is turned in a 
counter clockwise (to the left) direction, armature D is with¬ 
drawn from coil C, Figs. 334 and 335, which causes it to shunt 



DIAGRAM of CONNECTIONS TYPE.- H DS 
FOP M-P GENERAL-ELE.CTR.IQ COMPANY- 
CUP PENT PEGULflTOP. 

Figure 329J^. 

less flux, which has the effect of increasing current flow 
through secondary coil G, Figs. 334 and 335. In Fig. 334, E 
is an auto-transformer, F being the primary and G the 
secondary winding. A-A are the line and B-B the lamp leads. 

To Shut off Current, turn knob L, Fig. 333, clockwise (to 
the right) to “Low” point and then open the switch. 

AUTOMATIC REGULATOR.— The General Electric Co. 
also makes an automatic regulator called the Constant Cur¬ 
rent Regulator, Type RM. This is illustrated in Fig. 336 and 


































MANAGERS AND PROJECTIONISTS 


831 


its windings in 337. It is for use with the 30 ampere, 900 watt 
lamp, and has a regulation of 1 per cent., with (manufac¬ 
turer’s statement) an efficiency of 85 to 95 per cent. 

To Operate, separate the two coils of the auto-transformer, 
Figs. 336 and 337. Then throw in the line switch, after 
which let the twff coils come together gradually until the 
moving coil floats- freely. To turn off the current, separate 
the coils, pull switch and then move coils together again. 
The balancing weight has ball bearings, to insure freedom of 
movement. 

SYNCHRONOUS CONVERTER— To take care of the 
D. C. situation the General Electric Company puts out the 
“synchronous converter,” shown in Fig. 338. The motor re- 



Figure 330. 


ceives D. C. from the lines and delivers A. C. at about 25 
cycles to the lamp. This seems peculiar, because whereas in 
arc lamp projection we go to heavy expense to convert 
A. C. into D. C, in Mazda the reverse is true, and for best 
results we convert D. C. back into A. C. 

The synchronous converter has sufficient capacity to take 
care of the Mazda light source for two projectors. It is 
nothing more or less than a small synchronous converter 
connected up opposite to the way the synchronous converter 
is usually hooked up. It delivers A. C. at about 78 volts. 
It is about two feet in length, stands about one foot high and 
weighs something like 75 pounds. Its general care is covered 




832 HANDBOOK OF PROJECTION FOR 

under general instructions on motor generators, see Pages 
444 to 461. 

REGULATOR NECESSARY— Let it be clearly understood 
that a regulator is necessary where a synchronous con¬ 
verter is used, but in this case a special*regulator will be 
required, because the converter delivers current at lower 
voltage than the voltage of power lines. 

RHEOSTATIC CON¬ 
TROL. —In general, D. 
C. Mazda lamp installa¬ 
tions using rheostatic 
resistance are not rec¬ 
ommended. True, many 
of these installations 
have been made, and 
have given satisfaction 
to the exhibitor. They 
are not, however, rec- 
om mended by lamp 
manufacturers, nor do 
we recommend them. 
The manufacturer will 
make such an installa¬ 
tion if it is demanded, 
but for many reasons 
they recommend the 
synchronous converter, 
which, aside from first 
cost of installation, is 
much more efficient in 
operation than is rheo¬ 
static control. 

HALLBERG REGULATOR.— J. H. Hallberg manufactures 
an automatic regulator, for A. C. Mazda projector lamp in¬ 
stallations, called the “Hallberg A. C. 4 in 1 Mazda Lamp 
Regulator.” It is illustrated in Fig. 339. This regulator is 
constructed upon the constant current transformer prin¬ 
ciple. The secondary coil is stationary, while the primary 
coil is movable on a vertical central core This coil is sup¬ 
ported so as to be adjusted to the correct position on the 
core for each particular lamp, and any change in current 
strength over that for which the transformer is set causes 
the primary coil to automatically alter its distance from the 
secondary coil. It will therefore be seen that current 



Figure 331. 






MANAGERS AND PROJECTIONISTS 


833 


changes at the lamp filament will of necessity be very small. 

The device is supplied with an ammeter, and there is a 
conveniently located arrangement for adjusting the coils, or 
“setting” the coils for any desired current value within range 
of the apparatus. 

The Hallberg 4 in 1 is well made, and a good instrument 
of its kind. 

USING THE LAMP SETTER. —For the purpose of mount¬ 
ing the Mazda projector lamp in socket the General Electric 
Company puts out what is known as a “lamp setter,” illus- 



■k 


DIAGRAM of- CONNECTIONS TyPt- HMC 
PORM- 6 GENEPflL-ELECTRIC- COMPANY 


-CURP.5NT REGULATOR 


Figure 332. 


trated in Fig. 340. By the use of this setter it is possible to 
mount the lamp in its socket in such a way that an old lamp 
may be pulled out of the lamphouse and a new one installed, 
with every assurance that the filament of the new lamp will 
occupy precisely the same place with relation to the optical 
axis and the lens as did the old one; also the filament will be 
square with the face of the collector lens. To use the lamp 
setter, proceed as follows 

(A) Unscrew large nickel-head screw A, Figs. 340 and 341. 
until it is backed out to 7/16 of an inch. 

(B) Loosen small clamp screws B-B, Figs 340 and 341, on 
lamp socket. 














834 


HANDBOOK OF PROJECTION FOR 


(C) Unscrew center contact C, Fig. 341, until it is flush 
with bottom of socket base. 

(D) Insert lamp in socket, being sure to push it all the 
way down, at the same time making sure that the upper 
half of socket D-D, Figs. 340 and 341, moves freely in all 
directions, and that the lamp does not bind. 

(E) Unscrew two large knurled screws, E-E, Fig. 340, E, 
Fig. 342, and E, Fig. 343, and open gate F as shown in Fig. 
340. 

(F) Insert socket, with lamp in place therein, in lamp 
setter, and close gate F, Fig. 340. 



Figure 333. 


(G) Turn lamp in its socket until edges of filament are 
parallel with notch G, Fig. 342, and with the notch on oppo¬ 
site side of setter. 

(H) Look through sight holes H-H, Fig. 343, and raise 
lamp in center by screwing up on center contact from the 
bottom, as per Fig. 344, until bottom of filament coils is flush 
with lower edge of sight holes, as per Fig. 343. 

(I) According to which is necessary, tighten or loosen 
knurled adjusting screws E, Fig. 343, until the point of the 
two pins in bottom of sight holes come exactly between the 




MANAGERS AND PROJECTIONISTS 


835 


two center coils of the filament when you sight through the 
sight holes. 

(J) Should the filament not now be vertical, screw in or 
out, as the case may require, screw A, Figs. 340, 341 and 342, 
until filament is vertical, after which repeat operation I. 

(K) Tighten or loosen knurled head screw E, Figs. 340 and 
342, until the filament is in line with the two notches in gate, 
as per Fig. 342. This is the focusing adjustment. It locates 
the -filament the correct distance from face of collector lens. 

(L) Check vertical (height of lamp) lateral (location of 
pins between center coils of filament) and focusing (dis¬ 
tance from lens posi¬ 
tion) adjustments and 
be sure you have them 
EXACTLY right. 

(M) Tighten socket 
clamp D-D, Fig. 341, by 
screwing up socket 
clamp screws B-B, Figs. 

340 and 341, as sjhown 
in Fig. 345, thus locking 
the lamp in place in its 
socket. 

(N) Gently tighten up 
on center socket con¬ 
tact C, Fig. 341, as 
shown in Fig. 344, until 
it makes firm contact 
with base of lamp. This 
latter is important in 
order to secure good 
contact and prevent 
possible arc between 
lamp and socket. Be careful, however, and do not tighten 
the screw too tight, and thus force the lamp out of align¬ 
ment in socket. 

(O) Open gate F, Fig. 340, and unscrew knurled head 
screws E-E, Fig. 340, until they do not touch the lamp. 

(P) Check lateral adjustment, and if found wrong, correct 
same by tightening or loosening nickel-head screw A, Figs. 
340 and 341. 

(Q) Lamp and socket may now be removed from lamp 
setter, and may be inserted in base K, Fig. 346, with full 
assurance that if the various steps in the process (which is 
not at all complicated, once you learn it) have been faith- 



Figure 334. 




836 


HANDBOOK OF PROJECTION FOR 


fully and correctly followed, the lamp will be exactly in 
correct position for projection without further adjustment. 

ALIGNMENT.— TO SECURE MAXIMUM SCREEN IL¬ 
LUMINATION, IT IS ABSOLUTELY NECESSARY THAT 
THE CENTER OF LAMP FILAMENT, CENTER OF 
APERTURE AND CENTER OF PROJECTION LENS BE 
EXACTLY ON THE OPTICAL AXIS OF THE SYSTEM. 

CAUTION. —This is of very great importance with all 
Mazda projector lamp outfits because if any one of the 
elements named have its center even so much as 1/16 of 



■DWGMno^COMtCTIOMS- TYF&HMC 
-FOFM-fl GtNEKftLLLtCTR.Ki-COMP/IN't- 
- CUPPZaJT PteULflfOP, 

Figure 335. 

an inch off the optical axis the screen illumination will be 
very greatly reduced. 

To align the elements, first light the lamp and then open 
the dowser. Raise the automatic fire shutter or open the 
projector gate and turn projector fly-wheel until revolving 
shutter has opened the lens. Be sure lamphouse is all the 
way over against stop V, Figs. 327 and 330, in position for 
projecting motion pictures. 

Move the whole carriage Q, Fig. 347, carrying the regulator 
and lamphouse forward until the front surface of the pris¬ 
matic condenser is 6.5 inches from the aperture as per Fig. 























MANAGERS AND PROJECTIONISTS 


837 


351, except where state laws require a greater distance. 
Have a piece of dark colored, low reflecting cardboard held 
in front of the projection lens, at a distance therefrom which 
will sharply focus the rings of the condensing lens. Loosen' 
wing nuts Z-Z-Z-Z, Fig. 347 (four of them) and raise or 
lower the lamphouse until the same number of rings show, 
up and down, in the image on the cardboard, as per B, Fig. 
348. In other words, the 
image of the condenser 
is exactly centered up 
and down. Tighten 
wing nuts Z-Z-Z-Z 
firmly when done. 

Next move lamphouse 
sidewise on its tracks 
until the same number 
of rings show sidewise 
in the image on the 
cardboard, as per D, Fig. 

348, first, however, mak¬ 
ing certain that con¬ 
denser holder is shoved 
clear over against its 
stop S, Fig. 350. The 
lamphouse may then be 
moved sidewise by 
screwing or unscrewing 
the nickle-head screw 
W, Fig. 347. This screw 
must be against stop V 
when the job is done. 

Screw W must then be 
locked by set screw J, 

Fig. 347. This com¬ 
pletes the centering of 
the condenser with the 
optical axis. 

ADJUSTING FILAMENT OF LAMP ON OPTICAL 

AXIS.— It is of the very greatest importance imaginable that 
the center of the lamp filament be exactly on the optical axis 
of the optical train of the projector. Once a lamp has been 
adjusted in its socket in the lamp setter, as per instructions 
already given, and the filament has been centered on the 
optical axis, as per instructions we shall now give, all lamps 



Figure 336. 






838 


HANDBOOK OF PROJECTION FOR 


thereafter adjusted in the same lamp setter will require no 
further adjustment, unless the adjustment become in some 
way altered, which should not happen in ordinary routine 
of work. 

To center a lamp which has been previously properly ad¬ 
justed in the lamp setter (always adjust lamp in lamp setter 
before you proceed with the following instructions, because 
if you did not, your work would all be for nothing), proceed 
as follows: 

(A) Insert a lamp, previously adjusted in lamp setter as 


P/agfaft or Co/v/vrcT/ons 
SfOWM? Co/L 


JZ4T/0A 


1X500000000 

At?r COIL 

000000000 


r 


1///E IA/1P 


Gfwfxal £1fctf/c Co. foxst A?Ft 
CONSTANT CUFFFNT FfOULATOX FOX SO A'/ft? 

000 Watt Mazda Mot/on PtcruxF La/af 

Figure 337. 

per former instructions, in base K, Fig. 346, and shove it in 
as far as it will go. 

(B) When focusing, or adjusting a lamp for the first time, 
loosen mirror clamping knob X, Fig. 347, and tip mirror 
either up or down by means of handle Y, Fig. 347. 

(C) Place revolving shutter of projector from ^ to 1 inch 
from front end of projection lens barrel. 

(D) See that primsatic condenser lens is in proper position 
for projection and pull lamphouse over against stop V, 
Fig. 347. 

(E) Open dowser and either the automatic fire shutter 
or the projector mechanism gate. 

(F) Light the lamp. 











MANAGERS AND PROJECTIONISTS 839 

(G) Adjust projection lens so that edges of aperture are 
sharply focused on screen. 

(H) Set revolving shutter in such position that light beam 
falls on one of its blades, as per Fig. 349. The filament 
image will not necessarily be sharp. 

(I) Shove in or pull out the lamp socket by means of the 
small lateral adjustment screw L, on contact base K, Fig. 
346, until the two-center coils of the filament are exactly in 
center of lighted spot on shutter blade. 

IMPORTANT.— Do not touch large nickeled screw A, 
Fig. 350, on lamp socket. 

(J) Loosen socket base clamp T, Fig. 350, on steel plate 

carrying contact base, 
and move lamp forward 
and back until you get 
the smallest possible 
spot of light on aper¬ 
ture of projector, or 
until screen is brightest, 
though the screen will 
not at this stage of the 
proceedings be evenly 
illuminated. After this 
is done, tighten clamp 
screw T, Fig. 350. The 
distance of the filament 

from face of condenser will be found to be between and 
2inches, as per Fig. 350. 

(K) Test matter of filament being in center of spot on 
shutter blade. If too far to left screw in lateral adjustment 
screw L, Fig. 346, and shove lamp base further into its 
holder. If too far to right, reverse the procedure. If all 
directions have been faithfully followed the light should 
now be correctly centered on the projector aperture. If 
when filament image is in center of spot on shutter blade 
and spot at aperture of projector is out of center, then you 
have made some mistake and must do the whole job over 
again. But be certain the two center filament coil images 
are in center of spot on shutter. When lamp is properly set, 
lateral adjustment stop N, Fig. 350, above small screw K on 
contact base should firmly touch nickle screw A. Fig. 350, on 
lamp socket. Contact base is now properly set with respect 
to the lamp setter, and should require no further adjustment, 
but be sure the condenser slide and housing (these have to 
do with prismatic condensers only) are in correct position, 



Figure 338. 




840 


HANDBOOK OF PROJECTION FOR 



IMPORTANT— The lamphouse, the condenser and the 
lamp setter are now adjusted with relation to each other, 
so that all lamps adjusted in the individual lamp setter used 
should be, and will be in correct position when placed in the 
lamphouse. One lamp setter is suffcient for a number of pro¬ 
jectors. It should be clearly understood that the same lamp 
setter must be used for a lamphouse all the time, or if an¬ 
other setter be used, then the lamphouse will have to be 

readjusted to center the 
filament of the new 
lamp on the optical 
axis. 

(L) Close dowser T, 
Fig. 330, in the center of 
which is a pin hole, 
whereupon an image of 
the filament will be 
projected through the 
pin hole and will be 
clearly defined on the 
automatic fire shutter. 

CAUTION. —The pin 
hole must not be used 
in focusing the condens¬ 
ing lens or aligning 
lamp filament. It is 
only designed to serve 
as a method of checking 
the placing of the mir¬ 
ror with reference to 
the filament. 

The image projected 
through the pin hole 
will not necessarily be 
centered on the aper¬ 
ture, and the fact that 
it is off center with the 
aperture does not in¬ 
dicate that the line up 
of the condenser and 
lamp filament is incor¬ 
rect. Next move the 
mirror by means of 
knob Y, Fig. 347. By 
Figure 339. turning the knob clock- 








MANAGERS AND PROJECTIONISTS 841 

wise, the mirror image is made smaller and vice versa. 
This adjustment should be so made that the mirror image of 
the filament coils and the image of the filament coils are of 
exactly the same size. The mirror must now be so adjusted 
that the mirror image of the coils falls between the coils 
themselves, as per Fig. 320, whereupon the mirror must be 



Figure 340. 



Figure 341. 

locked rigidly in place by tightening knob, Fig. 347. Unless 
this adjustment be made right, the screen will be streaked 
vertically. 

With the mirror correctly set, it should never be necessary 
to change it, though its adjustment should be checked from 
time to time to make sure that it is in correct position. This 
the projectionist may observe at any time by glancing at the 
automatic fire shutter when the dowser is closed. It may 








842 HANDBOOK OF PROJECTION FOR 


also be observed on the revolving shutter while the pro¬ 
jector is in operation. 

If when a new lamp is installed, the mirror images do not 
fall exactly between the filament images, move the mirror 

slightly one 
way or the 
other until the 
fault is reme¬ 
died, but do 
not touch the 
lamp socket, or 
the adjusting 
contact screw 
N, Fig. 350. 


I M P O R - 
T ANT.—Never 
use anything 
except lever K 
and L, Fig. 347, 
to start up the 
lamp, or to 
turn it off. If 
you leave con¬ 
troller lever K 
a t “on,” and 
pull the pro- 
j e c t o r table 
switch, you will 
put the lamp 
out all right, 
and you may 
put it out of 
business for 
good, too. 


Figure 342. 


ADVANT- 
AGES OF 
MAZDA 
LAMP PRO¬ 
JECTION.— 
The main ad- 
vantage in 
Mazda lamp 
projection i s 
economy of 




















MANAGERS AND PROJECTIONISTS 


843 



operation. We can illustrate this advantage by comparison. 
Let us assume it is proposed to install Mazda lamp pro¬ 
jection in a theatre using 35 ampere D. C. arcs. This is not 
extreme because it is very generally conceded that the 
Mazda lamp 
can succesfully 
replace carbon 
arcs of much 
higher amper¬ 
age. Let us as¬ 
sume that the 
voltage of the 
arc is 55, under 
which condi¬ 
tion we would 
have 55 x 35 = 

1,925 watts 
consumed in 
the arc itself. 

This does not, 
however, rep¬ 
resent the total 
consumption of 
the installa¬ 
tion, since the 
line voltage, 
which may be 
110 or higher, 
must be re¬ 
duced to the 
arc voltage, or 
in other words 
to about 55 
volts. The 
most efficient 
method of do¬ 
ing this, and at 
the same time 
delivering the 
necessary am¬ 
perage at t h e 
arc, is by 
means of a mo¬ 


tor generator, 

and these ma- Figure 343. 














844 


HANDBOOK OF PROJECTION FOR 



chines cannot be expected to operate at greater than 70 
per cent, efficiency. As a matter of fact, a motor generator 
set usually operates at decidedly less than this, particularly 
after they have been used for a while. It therefore follows 
that the 1,925 watts consumed by the arc represents but 
70 per cent, of the total power consumed, which would be 
2,751 watts. 

On the other hand, the Mazda lamp equipment with which 

it is proposed to re¬ 
place this installation 
would consist of a 900 
watt T-20 bulb lamp, 
which operates at 30 
amperes and approx¬ 
imately 28-32 volts, so 
that we must reduce 
the line voltage to this 
value. A specially con¬ 
structed hand con¬ 
trolled regulator is 
made for this purpose, 
which operates a t 
(manufacturers’ 
claim) about 90 per 
cent, efficiency, hence 
the 900 watts con¬ 
sumed in the lamp 
represents 90 per cent, 
of the total power 
taken from the lines, 
that is, 1,000 watts. 


The difference i n 
wattage consumption 
would therefore be 
1,750 watts in favor of 
the Mazda lamp. 


We must, however, 
consider another item 
of cost, viz.: that of 
lamp renewal and car¬ 
bon consumption. It 
is impossible to give 
accurate figures in 
these items, but it is 
safe to assume that 


Figure 344. 











MANAGERS AND PROJECTIONISTS 


845 



the cost of necessary lamp renewals and of carbon con¬ 
sumption will be about equal. The saving through the 
use of Mazda equipment is, therefore, a matter of a dif¬ 
ference in current consumption. Supposing the theatre 
to be open ten hours a day, the cost of current for 
operating the carbon arc per year, assuming power to cost 
.07 cents per kw., equals .07 x 10 (hours per day) x 365 
2,750 watts consumed 

(days per year) x-— $703. The cost of 

1,000 

the Mazda on the other hand is .07 x 10 (hours per day) x 
1,000 watts 

365 (days per year) x - = $256, so that the actual 

1,000 

saving would be the difference between $703 and $256, which 
is $447 a year. 

The relative cost of 
any Mazda lamp and 
arc installation opera¬ 
tion may be calculated 
in the same way, 
merely by substituting 
the correct values, ex¬ 
cept that when the 
power lines supply di¬ 
rect current and A. C. 
is not available, it is 
then best to use a 
small synchronous 
converter (Fig. 338), 
which takes D. C. 
from the lines and de¬ 
livers A. C. to the 
lamp. The cost of op¬ 
eration of this form 
of installation is some¬ 
what higher than 
straight A. C., because 
of the higher cost of 
the converter, but it 
is much cheaper than 
taking D. C. through 
resistance. 

It therefore resolves 

itggjf into a problem, Figure 345. 







846 


HANDBOOK OF PROJECTION FOR 



in so far as finances go, as to whether the screen results will 
be such that the drawing power of the theatre will not be 
materially decreased, because it would require but a slight 
loss in drawing power at the box office to amount to 
the sum saved in current. 

There are, however, sev¬ 
eral other advantages in 
Mazda lamp equipment. 

For instance, with Mazda 
lamps there is nothing like 
as much heat dissipated 
in the projection room, 
therefore the work of the 
projectionist is made very 
much more comfortable. 

Also with Mazda lamps 
the light source is abso¬ 
lutely steady, and once it 


Figure 346. 



Figure 347. 


is properly 
adjusted and 
set going it 
requires no at¬ 
tention what¬ 
ever through¬ 
out the run, 
unless the sup¬ 
ply voltage 
fluctuates 
heavily. With 
the carbon arc 
install ation 
there is a cer¬ 
tain amount of 
carbon dust set 
free in the air, 
which besides 
setting up a 
more or less 
unhealthy con¬ 
dition for the 
p r o j ectionist, 
gets into the 










MANAGERS AND PROJECTIONISTS 


847 


bearings of a projector and causes considerable wear. Then, 
too, there is the white ash which is the product of the 
volatilization of the carbon cores, and there is more or less 
carbon monoxide gas which is not especially healthful, 



Figure 348. 







848 


HANDBOOK OF PROJECTION FOR 


though as a matter of fact most of it is nowadays carried 
outside of the projection room. Everything considered, it 
cannot be denied that the Mazda light source is more health¬ 
ful and comfortable to work with than is the arc light. 

NOT SIMPLE. —Many projectionists have objected ton 
Mazda lamp projection because they believed it would not 



Figure 349. 

require much skill to handle, therefore it could be handled 
by a man of little experience or knowledge. This is a mis¬ 
taken idea. While it is true that once adjusted the Mazda 
lamp is rather simple and easy to manipulate, still its ad¬ 
justment is a very much finer operation than is the adjust¬ 
ment of the carbon arc. It takes real brains and intelligence 
to get the best possible results out of a Mazda Motion 
Picture Projector Lamp since it is essential that every pos¬ 
sible bit of illumination be got through to the screen. 




MANAGERS AND PROJECTIONISTS 


849 


Another distinct advantage is that with Mazda lamp pro- 
jectibn the projectionist really has nothing to do but watch 
his screen and attend to the projection of the picture, which, 
after all, is the important thing. 

The advantages claimed for Mazda lamp projection may be 
summed up in the following: 



Figure 350. 


1. Economy of operation. 

2. Steady light. 

3. Soft, pleasing light. 

4. Easy of operation. 


Reduction of current bills 
from 30 to 60 per cent. 

No variation in light inten¬ 
sity. 

No harsh blue light. 

Lamp once set needs no fur¬ 
ther attention until re¬ 
moval. 










OPTI CfIL Sy^Ttn *>e MflZDfl • MOTION PI CTO Ht PPOJtCTION■ 


850 


HANDBOOK OF PROJECTION FOR 



Figure 351. 


































MANAGERS AND PROJECTIONISTS 


851 


5. Prevents excessive heat in 

projection room. 

6. Healthful operating condi¬ 

tions. 

7. Longer life of projector 

parts. 


Wattage dissipated in heat 
much lower than that of 
arc. 

No carbon dust or fumes for 
projectionist to inhale. 

No carbon dust to wear bear¬ 
ings. 


Fig. 351 is a graphic illustration of the Mazda lamp line 
up, the distances therein are all a fixed quantity when using 
prismatic condensers. 


The following is a tabulation of the possible causes and 
remedies of unsatisfactory screen illumination: 


Remedy. 

Operate at rated amperage. 


Trouble. 

1. Lamps operated under 

amperage. 

2. Optical system out of 

alignment. 

3. Lamp burned beyond its 

useful life. 

4. Dirty mirror and lenses. 


5. Number one or quarter 

size projection lenses, 
1 inch diameter. 

6. Incorrect distances be¬ 

tween parts of optical 
system. 

7. Three-wing shutter. 

8. Wrong type of screen. 

The following 
remedies of low average 

1. Ammeter out of adjust¬ 

ment. 

2. Improper method of light¬ 

ing lamps. 


See Method of Proper Align¬ 
ment of Optical System. 

New lamp. 

Clean mirror and condenser 
thoroughly every day. 

See “Cleaning Lenses,” Page 
137. 

Use number two or half size 
lenses 2 y 2 inch diameter 
whenever possible, i. e., 
where focal length is 5 
inches or greater. 

See method for proper align¬ 
ment of optical system. 

Use a two-wing shutter. 

Use screen suitable to the re¬ 
quirements of theatre. 


Correct by checking with 
standard ammeter. 

Always use handle on regu¬ 
lator to avoid initial 
surge of current. 


is a tabulation of the probable causes and 
life of lamps: 


The following is a tabulation of the probable causes and 
remedies of uneven screen illumination; 


852 


HANDBOOK OF PROJECTION FOR 


1. Incorrect setting of mir¬ 

ror. 

2. Lamp filament badly 

warped out of parallel, 
or a small section short 
circuited. 

3. Condenser lens out of 

alignment. 


Correct setting. See method 
for proper alignment of 
optical system. 

New lamp. 


See method for proper align¬ 
ment of optical system. 


THE PLANO-CONVEX CONDENSING SYSTEM.— The 

Precision Machine Company, makers of the Simplex pro¬ 
fessional projector, manufacture a Mazda equipment which 
employs a plano-convex condenser, exactly the same as the 
plano-convex condenser used in arc light projection. A 
general view of the Simplex Mazda outfit, with lamphouse 
doors removed and the condenser casing open, is had in Fig. 
352, in which Q is'the swinging projector table, exactly the 
same as is used to support the Simplex Type S lamphouse, 
or other Simplex arc lamphouses. 

To replace the arc lamphouse with a Mazda lamphouse it 
is only necessary to remove the former and set the latter in 






















MANAGERS AND PROJECTIONISTS 


853 


its place, being sure the base of the Mazda fits down into the 
grooves properly. When the Mazda lamphouse is in place, be 
sure and tighten wing-nuts (two of them) R, Fig. 352, which 
locks it to the swinging table. 

The CONDENSER. —The Mazda plano-convex condenser, 
as used by the Simplex, consists of a 6inch focal length 
collector lens (lens next the lamp) and a inch focal length 
converging lens (lens next aperture), both of standard 4 
inch diameter. These lenses are so placed that they are 
only 1/16 of an inch apart, as shown in Fig. 362. The focal 
lengths named are never changed. A 6combination is 
the standard Simplex Mazda condenser. 

CAUTION. —Be sure there is not to exceed 1/16 of an inch 
between the apexes of the curved surfaces of the lenses, as 
shown in Fig. 362, because spacing the lenses further apart 
alters the E. F. of the condenser combination and throws 
everything out. 

The lenses are held in metal rings, exactly the same as 


WIRING DIAGRAM FOR SINGLE LAMP EQUIPMENT 
DIRECT CURRENT 



LEAD 3' CTLONG MACHINE SWITCH 


PRECISION MACHINE CO.INC. 
317-323 EAST 34 ST. NEW YORK.N.Y 


Figure 353. 































854 


HANDBOOK OF PROJECTION FOR 


those used for Simplex arc light condenser lenses. They 
are fully described on Page 663. 

CAUTION. —Do not screw the retaining ring down tight. If 
you do you will clamp the lens and there will be no room for 
expansion, which may result in breakage. A good rule is to 
screw the retaining ring down tight and then back it off 
about half a turn. 

ADVANTAGES. —The advantages claimed by the manufac¬ 
turer for the piano convex method of condensing Mazda 
light are (A) greater distance from condenser to aperture. 
(B) Less divergence of light beam between aperture and 
condensing lens because of greater distance condenser to 
aperture. (C) The same condenser may be used for both 
motion picture and stereopticon projection where a combi¬ 
nation projector is used. (D) All adjusting handles are on 
the outside of the lamphouse. (E) The method by means 
of which a new lamp is inserted when an old one burns out, 


WIRING DIAGRAM FOR SINGLE LAMP EQUIPMENT 
SIMPLEX AUTOMATIC A.C.REGULATOR 
FOR MAZDA 900 WATT 30 VOLT 30 AMP LAMP 
LINE 95-120 VOLTS 60 CYCLE 


AMMETER 
NO.8 WIRE 0 
REGULATORS^ 



CHANGE OVER J 
SWITCH 


NO. 12 WIRE 






LINE 95-120 VOLTS 
60 CYCLE 




NO. 8 ASBESTOS WIRE 
NO.8. ASBESTOS WIRE 
OR NO. 8 STAGE CABLE- 
NC?rE-IF VOLTAGE IS BELOW 100 
USE N0S.2 5 3 LEADS INSTEAD OF 
NOS.I 5 3 


15 AMR FUSES PRECISION MACHINE C0.INC. 

317-323 EAST 34 ST. NEW Y0RK.N.Y. 


Figure 354. 




































MANAGERS AND PROJECTIONISTS 


855 


and the manner in which lining the filament with relation 
to the lens system. 

CURRENT CONTROL. —In order that continuity in action 
may be had we shall place a description of the current con¬ 
trol here, because before attempting some of the operations 
described further along it is necessary that current be avail¬ 
able at the lamp. 

Where the current supply is D. C. the Simplex Mazda lamp 
takes current through an adjustable rheostat, which has such 
fine adjustments that very slight changes in current (amper¬ 
age) may be made by the projectionist. This apparatus is 
illustrated in Fig. 353, in which the method of wiring is 
shown, A being the amperage regulator. Do your wiring 
according to the diagram in Fig. 353 and you will be correct. 

If the current supply be A. C., then a Westinghouse trans¬ 
former, called an “automatic regulator,” is used. This ap¬ 
paratus is so arranged that it acts automatically to keep the 
current flow at the rated capacity of the lamp, regardless of 


WIRING DIAGRAM FOR TWO LAMP EQUIPMENT 
SIMPLEX AUTOMATIC A.C.REGULATOR 
FOR MAZDA 900 WATT 30 VOLT 30 AMR LAMPS 
LINE 95-120 VOLTS 60 CYCLE 


NO.8 ASBESTOS WIRE 
OR NO. 8 STAGE CABLE 
CHANGE OVER AMMETER 
SWITCH NO.8 WIRE 

REGULATOR 

N0TE- 
1F VOLTAGE 
IS BELOW 100 
USE NOS. 2 & 

3 LEADS *- 
INSTEAD OF 
N0S1 X 3 



LINE 95-120 VOLTS 
60 CYCLE 



15 AMP FUSES PRECISION MACHINE C0.INC. 

317-323 EAST 34 ST. NEW Y0RK.N.Y. 


Figure 355. 















































856 


HANDBOOK OF PROJECTION FOR 


fluctuations in voltage. The device is unique, in that it may 
be set to deliver any desired amperage within the range of 
its capacity, and once so set and locked for a given current 
flow (merely the matter of moving a handle on the end of 
the device up or down until the desired amperage flow is 
accomplished, and the giving of the aforesaid handle a twist 
to lock it) it will maintain that amperage until the adjust¬ 
ment is changed. 

It is also unique in that by the closing of a contact device 
it will deliver sufficient additional current to heat the fila- 



TO JLflMP 


FRONT END OF 
REGULATOR 


REAR END OF 

regulator 


Figure 356. 


ment of the idle lamp of a two-lamp installation, without 
affecting the operation of the lamp on the working pro¬ 
jector. 

The regulator is a step-down transformer, the primary 
coil of which moves and automatically changes its distance 
from the secondary coil when there is change in supply 
voltage, or other cause tending to alter the current flow at 
the lamp. 

CONNECTING REGULATOR.— The connections for a 
single and two-lamp installations are shown in Figs. 354 and 
355. Connect the line wires, through a D. P. S. T. knife 








MANAGERS AND PROJECTIONISTS 


857 


switch, of sufficient capacity, and 20 ampere fuses if the cur¬ 
rent be 110 volts (if 220 volts, then use 10 ampere fuses) to 
the terminals marked “LINE” at bottom of regular panel. 

CAUTION.—Regulators must not be used on any voltage 
or current frequency except as per markings on name plate 
of each regulator. 

Connect terminals on regulator panel marked “METER” 



Figure 357. 

to terminals of ammeter. If no ammeter is used (which 
should never be the case), then connect the terminals 
marked “METER” to each other, using either a good con¬ 
nector (see Fig. 26, page 122) or else solder the joint. 

CAUTION.—For good and sufficient reason it is necessary 
that the ammeter be located at least two feet away from the 
regulator. We strongly advise that it is located where it 














858 


HANDBOOK OF PROJECTION FOR 


will be in constant view of the projectionist when in position 
beside the projector. We recommend, and strongly too, that 
two ammeters be used, one located beside or immediately 
over each observation port. The extra ammeter will soon pay 
for itself in the saving effected in lamp filaments through 
consequent close regulation of the current induced by having 
an ammeter at all times directly under the observation of the 
projectionist. 

Connect panel terminals marked “LAMP NO. 1” and 
“LAMP NO. 2” to the respective projector lamps through the 
projector table switches (the left-hand projector being, 



Figure 358. 
















MANAGERS AND PROJECTIONISTS 


859 


usually, merely as a convenience in designation, called pro¬ 
jector No. 1), which finishes the job. 

OPERATION OF REGULATOR.— By examining Fig. 356 
you may see the location of all the various terminals and 
switches, but we will tell you the location anyhow. The 
transfer switch, located on front of regulator, cuts in either 
lamp on a low current circuit for the purpose of warming up 
its filament preparatory to switching the lamp to full amper¬ 
age. This is for two purposes: (A) To eliminate the shock 
attendant upon turning full current strength into a cold lamp 
filament. (B) To enable the projectionist to light the lamp 
of the idle projector while the other lamp is operating, in 
order to make any adjustments of the apparatus which may 
seem necessary. 

When the transfer switch is thrown to the right—right 
when looking at the panel board—lamp No. 1 is connected to 
the main secondary coil, and is at full amperage, while lamp 
No. 2 is connected to what is then the auxiliary secondary 
winding, at low amperage, for warming up. 

The line voltage switch, handle of which projects through 
the terminal board cover, enables the regulator to operate 
under a considerable range of supply line voltage. 

IMPORTANT. —The line voltage switch must always be 
kept in such position as will prevent the moving coil from re¬ 
maining in contact with the stop at either end of its travel. 
As a measure of safety, for lamp protection, the Simplex 
people recommend that it be kept at “LOW,” except when 
conditions indicate that the position should be changed. AL¬ 
WAYS HAVE THIS SWITCH AT I )W‘WHEN STARTING 
THE LAMP. 

TO START LAMP IN OPERATION.— Let us assume we 
propose using projector No. 1—the left-hand projector. First 
of all throw transfer switch to the left, and line voltage 
switch to the position marked “LOW.” If it is the first time 
we have used the apparatus, set the adjusting handle to 
position marked “30” on scale, which means 30 amperes. 
Close line switch. Close table switch of projector No. 1, and 
as soon as lamp filament has come to a glow for about one 
second (longer will do no harm, but one second is quite suffi¬ 
cient for the purpose) throw transfer switch to the right and 
immediately examine position of moving coil, though this 
latter is only necessary occasionally, once the apparatus is 
adjusted, or after installing a new lamp. 

If it is found the moving coil is against, or is too close to 


860 


HANDBOOK OF PROJECTION FOR 


one of the stops, immediately adjust the line voltage switcn, 
as before directed. > 

IMPORTANT.—A few seconds before it is time to change 
over from one projector to the other, close table switch of 
idle projector in order to heat up the filament of idle lamp 
preparatory to switching it to full current capacity. The 
change from one lamp to the other, aside from the low 
amperage heating-up current, is accomplished by throwing 
transfer switch to opposite position. 

CAUTION.— After installing a new lamp, always examine 
the ammeter, and by means of the adjusting switch, so regu¬ 
late the current flow that it is just 30 amperes. 



IT IS ESSENTIAL THAT AN AMMETER BE USED. 
The adjusting switch scale may be depended upon for a fair 
degree of accuracy, but that is not sufficient. If you want 
maximum service from your lamps you must have EXACT 
accuracy, and that may only be secured by the use of a good 
ammeter. 

TAKE NOTICE.—We strongly recommend that users of 
Mazda projector lamps have their ammeters tested at least 
once a year. It will pay you to do it. An ammeter register¬ 
ing low will cause constant overloading of your lamp fila¬ 
ments, and thus very greatly shorten the life of the lamps. 

We would also caution you against deliberate overloading 
of lamp filaments. The projectionist may get much more 



























MANAGERS AND PROJECTIONISTS 


861 


light all the time by boosting the amperage above the rated 
capacity of the lamp, or he may boost it when a dense 
scene comes through, but if he does so he has no right to 
complain if the lamp filaments warp, sag or burn out very 
quickly, or at least last very much less than their estimated 
span of life. 

Never use such an outfit as is shown in Fig. 353, except for 
D. C. If your current is A. C. use the regulator. The rheostat 
may be used on A. C., yes, but by comparison with the 
regulator it is extremely wasteful. 

THE LAMP HOLDER. —The lamp used is a 900 watt, 30 
ampere, 30 volt Tungsten filament lamp. The coils of such 
a lamp are shown, full size Fig. 317. The lamp is held in a 
socket Z, Fig. 357, very similiar to the ordinary lamp socket, 
except that the lower central contact of the socket is mov¬ 
able, or adjustable as to its height. 

Examining Figs. 357 and 358 you will note knurled-head 
thumb screw H. The upper end of this screw presses against 
a spring blade, which is raised as the thumbscrew H is 
screwed in, and is lowered as it is screwed out, or down. The 
center contact of the lamp makes contact with this spring 
blade which carries current to the lamp from one side of the 
line. The need for this adjustment is as follows: When the 
lamp is inserted it is screwed into the socket as far as it will 
go, but in this position it is probable the filament will not 
face the lens squarely. It will therefore be necessary to un¬ 
screw it a part of a turn, which has the effect of altering the 
distance the center contact of the lamp will be from the 
bottom of the socket when it, the lamp, is in operating po¬ 
sition. From this you will understand the need for the cen¬ 
ter contact of the lamp being adjustable as to height. The 
detail of this contact is diagramatically illustrated at A, Fig. 
359. The lamp holder, as a seperate unit, is shown in Fig. 357. 

TO PLACE LAMP IN HOLDER.— First lower knob H, 
Fig. 357, as far as it will go. Then screw lamp into socket as 
far as it will go, then see if the face of the filament is paral¬ 
lel with (in line with) knob F. Fig. 360, and the shaft it 
controls. If not, then unscrew the lamp from the socket 
enough so that the filament is in line, whereupon tighten the 
knob H, Figs. 357 and 358 until firm contact is made with 
base of lamp. The tightening of knob H serves two important 
purposes, viz.: (A) It forms electrical contact between the 
lamp base and contact strip, as per Fig. 359. (B) It locks the 
lamp into the socket, thus making good electrical contact 


862 


HANDBOOK OF PROJECTION FOR 



Figure 360. 

















MANAGERS AND PROJECTIONISTS 


863 


between the metal of the socket and the metal of the lamp 
base. You therefore will understand the importance of setting 
knob H up firmly. 

PLACING LAMP IN LAMPHOUSE. —Each lamp must first 
be placed in a holder as per preceding instruction, and the 
holder afterward installed on the lamp base in the lamp- 
house. The method of connecting the holder to the base is 
simple; also its removal from the base is equally simple. To 
install a holder containing lamp, proceed as follows. In Fig. 



Figure 361. 


358 you see contact strip V. At A, Fig. 359 you see what 
it is and what it connects to. In Fig. 360 you see the side 
of lamp holder opposite to the side shown in Figs. 358 and 361, 
and at B, Fig. 359, you see a drawing of the back end of the 
lamp holder. As shown at B, Fig 359, threaded collar U, Fig. 
36Q, is really a hollow shaft, on the opposite end of which 
knob F, Fig. 358, is mounted. 

To insert the lamp holder, shove it past knob E, Figs. 358 
and 361 and engage contact strip V, Fig. 358, with slot in 
part W ? as shown, at the same time entering a stud which 

















864 


HANDBOOK OF PROJECTION FOR 


protrudes from lug Y, Fig. 360, into the hole in end of 
threaded collar U, Fig. 360, and shove the holder in as far 
as it will go. 

By way of explanation, a metal stud passes through and is 
gripped and held by lug Y, Fig. 360. To one end of this stud 
wire X attaches, as shown. The other end extends beyond 
the left hand end of lug Y to a considerable distance, and 
forms the support for one side of the lamp holder. It also 
forms the current carrying connection between wire X and 
lamp socket Z, Fig. 360. 

CAUTION.—After inserting lamp holder, be sure and tighten 
thumbscrew G, Fig. 360, which locks parts S and stud into 
good electrical contact. Unless this be done there may be 
arcing between the two parts, which may, in time, either 
injure or ruin them. 

THE MIRROR. —In order that the light from the back side 
of the filament be not wasted, and that the light source pre¬ 
sent to the lens a solid, unbroken surface, a spherical mirror 
is employed, placed as per Figs. 360 and 362. The reasons 
for this mirror, and an explanation of its action will be found 
in the text matter, page 819. 

It is of course vitally important that the mirror be so 
placed that the image it reflects, or projects, will fall exactly 
in its appointed place, and the Simplex equipment provides 
ample adjustments, in convenient form, to enable the projec¬ 
tionist to place the image exactly where he wants it. 

CLEANLINESS. —It is essential to efficient results that the 
mirror be kept perfectly clean. You must polish its surface 
daily. This may be done by washing it with a solution of half 
wood alcohol and half water, or with gasoline, polishing the 
surface while still wet. It may also be done by breathing on 
surface while mirror is still cold, and polishing with a per¬ 
fectly clean, soft cloth, or with tissue paper. 

We would recommend to theatre managers that they pro¬ 
vide, for the purpose of cleaning lenses, a roll of soft high 
grade toilet paper. Such paper is most excellent for the pur¬ 
pose, and clean lenses mean much in excellence of screen 
results. 

To remove or insert a mirror it is only necessary to loosen 
thumb screws X-X-X (three of them), and insert or take 
out the mirror, as the case may be. 

CAUTION. —After inserting a mirror, be sure to tighten 
thumb screws X-X-X, but only sufficiently to hold the mirror 
in position, without exerting undue pressure. DON’T jam the 


MANAGERS AND PROJECTIONISTS 


865 


thumb screws down tight, unless you want a broken mirror. 

DISTANCE.—FILAMENT TO MIRROR.— Distance center 
of back of mirror from lamp filament must be as shown in 
optical diagram, Fig. 362. This is important to good results 
The correct distance may be obtained by turning knob A, 
Fig. 361 in the required direction. 

Having placed the mirror in position and secured the cor¬ 
rect distance back of mirror to lamp filament, unlock the 
mirror by turning knob D, Fig. 361, to the left, and swing the 
mirror to one side as far as it will go by means of knob G, 
Fig. 361, locking it there by means of knob D. This is to 
prevent focusing the filament image, which is not desired 
at this stage of the proceedings. 



Figure 362. 

LOCATING THE LAMP FILAMENT IMAGE.— In the 

center of the douser is a pin hole. Light your lamp and you 
will find an image of the lamp filament projected through the 
pinhole to the automatic fire shutter, upon which it must be 
centered. Should the image be either too high or too low, it 
may be raised or lowered by means of knob E, Figs. 352 and 
361, which raises or lowers the lamp as a whole. The image 
may then be centered sidewise by first loosening thumbscrew 
G, Fig. 360, and turning knob F, which moves the lamp side- 
wise. 





















866 


HANDBOOK OF PROJECTION FOR 


NOTICE. —If it is desired to move the lamp toward you it 
is only necessary to turn knob F to the right, but if you wish 
to move the lamp from you you must turn knob F to the left, 
and at the same time shove the lamp holder in. This is because 
the threads on threaded collar U, Fig. 360, engage with 
threads in part S, Fig. 360, while collar U merely butts up 
against the end of lug Y, hence turning knob F to the right 
will pull the lamp back, turning it to the left will have no 
effect, unless you shove in on the holder at the same time. 
Examine the parts and you will see how it works. Be sure 
and tighten thumbscrew G, Fig. 360, when you are through. 

FOCAL DISTANCES. —Examining the optical diagram, Fig. 
362, you will see what the focal distances must be. They are 
the distances recommended by the manufacturer of the ap¬ 
paratus, who certainly should know what is best. You doubt¬ 
less will be inclined to question the recommendation of nine 
inches from front surface of condenser to aperture when a 
small diameter projection lens and eleven inches when a 
large diameter projection lens is used, since this is exactly 
opposite to the usual condition recommended, but the figures 
are correct nevertheless. The apparent contradiction in dis¬ 
tances is due to the fact that the longer distance with the 
larger lens is necessary in order to overcome chromatic aber¬ 
ration. 

CAUTION.—DON’T guess at distances. Use a ruler and get 
them exactly right. You are not working with an arc lamp 
now, and cannot make surplus light available to offset the 
waste attendant on “guess work,” therefore stop guessing 
and do your work right if you want satisfactory results. 

LOCATING FILAMENT.— The lamp filament must be 35/ s 
inches from the face of the collector lens, as per Fig. 362. By 
means of knob B, Fig. 361, move the lamp backward or 
forward until, using a ruler, you have the filament exactly 
that distance from the face of the lens. When you get the 
filament the right distance, close the lamphouse door and 
move the filament locater in the lamphouse door backward 
or forward until you can see the lamp filament through it, 
whereupon tighten the holding screws of the locator. This 
device is to enable you to place the filaments of new lamps 
you install the correct distance from the lens. Once set, as 
above, when you install a new lamp you have but to move 
it backward or forward until the filament can be seen 
through the locator tube, and it is exactly the right distance 


MANAGERS AND PROJECTIONISTS 


867 


from the lens. It is very important that this distance be pre¬ 
cisely right. 

FOCUSING LAMP FILAMENT.— If you have followed the 
instructions to this point, you have the lamp installed, its 
filament correctly centered with the aperture and at the 
right distance from the collector lens. You must now proceed 
to focus the filament as follows: Remove the projection lens, 
open the automatic fire shutter and block it up so that the 
aperture is open (no film in projector of course) and move 
the revolving shutter out on its shaft until its blade is exactly 



Figure 363. 

10J4 inches from the aperture. Instead of moving the shutter 
you may, if you prefer, support a piece of dark colored card¬ 
board or sheet metal 10*4 inches from the aperture to serve 
as a screen. Now light the lamp and you will find an image of 
the lamp filkment on the shutter blade or the cardboard 
screen, as per A, Fig 363. By means of knob B, Fig 361, move 
the lamp, as a whole, backward or forward on its base until 
the filament image is as sharp as you can get it. 

FOCUSING THE MIRROR IMAGE.— When you have the 
filament image sharp, unlock the mirror by turning knob D, 
Fig. 361, to the left, and by means of knob C swing the mirror 






868 


HANDBOOK OF PROJECTION FOR 


over until the mirror image of the filaments appears on the 
shutter blade or cardboard screen. This image will be much 
less brilliant that the filament image itself. 

Next, by turning knob A, Fig. 361, we make the mirror image 
as sharp as possible and then, using knob C, Fig 361, which 
swings the mirror sidewise, and knob D, Fig. 361, which 
causes the image to raise or lower, so locate the mirror 
image that it exactly fills the space between the filament 
coils, so that the image appears as at B, Fig 363. 

Now replace the projection lens, and lock the mirror in 
place by means of knob D, Fig 361, and the job is finished. 

The entire adjustment should now be complete and correct, 
and the screen field should be clear. Should there be discolor¬ 
ation, slowly move the entire lamphouse backward or for¬ 
ward until it disappears, after which tighten wing-nuts (two 
of them) R, Fig 352. 

NOTE—It is quite possible to complete the entire placing 
and focusing of both filament and mirror images on the 
automatic fire shutter, using the pin hole in the douser, but 
experts at the Simplex factory tell us the revolving shutter 
blade or card board screen gives more accurate results. 

EXTRA LAMPS.— It is necessary, or at least highly advis¬ 
able that one or more extra lamps be on hand, adjusted in 
spare lamp holders and all ready for immediate insertion in 
the lamphouse. Failure to take this precaution may, and 
probably will cause an embarrassing situation as the audience 
waits while you install a lamp in its holder, and the holder in 
the lamphouse, the first named proceeding probably requiring 
a longer period of time that the second. 

INSTALLING EXTRA LAMP IN LAMPHOUSE.—First, 

before attempting to remove the old lamp, be sure the pro¬ 
jector table switch is “open.” Then, having the spare lamp 
properly installed in its socket, as per instruction already 
given, loosen thumb screw, C, Fig. 360, and pull old lamp and 
its holder out, after which insert the holder with new lamp as 
per instruction : “Placing Lamp in Lamphouse.” Next close pro¬ 
jector table switch, bring lamp up to normal amperage, center 
filament image on automatic fire shutter and mirror image be¬ 
tween coils. Resume projection, and, if necessary, move lamp- 
house backward or forward to get as clear a field as possible 
until opportunity is had to complete a perfect adjustment. 

NOTE.—If current be D. C. move regulator to “Low” as soon 
as projector table switch is pulled. If current is A. C. set 


MANAGERS AND PROJECTIONISTS 869 

regular line voltage switch at “LOW” as soon as table switch 
is pulled. 

COMPARISON OF CRATERS.— The General Electric Com¬ 
pany has provided us with the data needed for intelligent 
comparison of the ordinary and the high intensity arc. This 
data is found in the following table, which is self explanatory, 
insofar as undertanding its data goes: 




Carbon 

Crater 

Crater 

Lumins 

Avg. Ft. 
Candles on 

Kind of 
arc 

Amperage 

diameter 

diameter 

Depth 

in Beam 

Screen 

Low 

Intensity 

50 

3/4 Pos. 
5/16 Neg. 

.47" 

.12" 

688 

5.83 

Low 

Intensity 

75 

7/8 Pos. 
13/32 Neg. 

.56" 

.17" 

1035 

8.77 

Low 

Intensity 

100 

1" Pos. 

9/16 Neg. 

.66" 

.55" 

1480 

12.55 

High 

Intensity 

50 

9 mm Pos. 

9 mm Neg. 

.27" 

.05" 

1437 

12.2 

High 

Intensity 

75 

11 mm Pos. 
11 mm Neg. 

.35" 

.11" 

2700 

22.9 

High 

Intensity 

120 

13.7 Pos. 

11 mm Neg. 

.48" 

.34" 

4950 

41.9 


Condensers used for tests SA and piano convex. 

Projection lens 5" E.F., 1 7/16 Dia. Speed F 3.4. 

Screen 9' 7" x 12' 4". 

NOTE.—1 mm equals .03937 of an inch. 

This data was received after the rest of the high intensity 
data was compiled. It is interesting to observe the great 
difference in carbon size and crater diameter. For equal 
amperage it will be observed that the crater diameter is but 
little more than one-half for the high intensity. This should en¬ 
able the projectionist to retard his condenser, use a short 
focal length condenser and reduce the beam divergence be¬ 
yond the aperture to a value which will enable the projec¬ 
tion lens to pick up the entire beam from a 120 ampere arc, 
a thing which will be highly beneficial in more than one way. 


ARMS AND LEGS ARE 
CHEAP — USE YOUR 
BRAINS. 






870 


HANDBOOK OF PROJECTION FOR 


Weaver Douser 

A N ELECTRIC DOUSER— The change-over is facilitated 
by what is known as the Weaver Electric Douser, which 
works by magnetic action and cuts off the light from one 
projector, substituting that of the other simultaneously, or at 
least in the very small fraction of a second. The action is in 
fact so rapid that it is practically instantaneous. 



Figure 363-A. 

In Fig. 363-A we have the photographic view of the douser, 
and in Figs. 363-B and 363-C wiring diagrams for two and 
three-projector installations. It is also quite possible to add 
other switches, so that the douser may be set into action from 
any desired point in the projection room, though this latter we 









MANAGERS AND PROJECTIONISTS 871 

do not either value or recommend, because we hold that the 
projectionist should be beside the projector, where he rightly 
belongs when a picture is being projected. 

The douser is clamped to the front of the condenser cone 
by means of ring A, Fig. 363-A. The method of attachment is 
made quite evident from an examination of the picture. One 
push button switch is located on or near to each projector. 
It is possible to locate other push buttons at the re-winder 
table or elsewhere, if desired. These switches must, how¬ 
ever, be of such type as will make contact ONLY when the 
button is pressed down. If the current be D C, then it is 
advisable to use an “H and H” switch. In any event if the 
current be D C a switch which will not arc must be selected. 
If the current be alternating, then any type of momentary 
contact may be used. 

CAUTION.—Switch should always be kept lubricated to 
prevent possibility of sticking'. The douser circuit must be 
fused, and the fuses must not exceed ten (10) amperes 
capacity. 

Wires attached to douser are colored. Yellow wire con¬ 
nects douser to line, through a S. P. S. T. knife switch. Light 



WIRING PLAN-TWO DOWSERS - TWO SWITCHES 
Figure 363-B. 































872 


HANDBOOK OF PROJECTION FOR 


brown wire closes douser. It is attached to white wire of 
other douser, and through it to one terminal of each switch, 
as shown. 

White wire connects to brown wire of other dousers, and 
through it to one pole of each switch. The third pole of the 
switches connects to the line. It is all made very plain in 
Figs. 363-B and 363-C. 

CAUTION. —Before connecting white and light brown wires 
to switches, test the circuits and see that they are open 
except when switches are operated. All momentary contact 
switches have two “hot” legs. They are sometimes bridged 
across one end and sometimes from corner to corner. Always 



WIRING PlAN-THREE DOWSERS - THREE SWITCHES 
Patented Feb. 1. 1921 

Figure 363-C. 


test to determine which, as it will make a difference in 
necessary connections to switch. Diagrams show H and H 
switches which are bridged across from corner to corner. 

Should dousers open or close too far, or not far enough, 
loosen lock nuts at end of coil box and screw the brass 
bumpers in or out, as need may be until the correct adjust¬ 
ment is had. 

Should douser fail to remain open while projector is in 
operation, remove taper pin in slot, stretch spring to give it 
more tension, and replace. 

TO OPERATE.— The douser may be operated by hand 
whenever desired. The hand operation of one douser will in 
no way affect the other. To operate electrically, push button 
of switch and release IMMEDIATELY. 















































MANAGERS AND PROJECTIONISTS 


873 


Automatic Curtain Machine 

L T NDER many conditions there can be no question but 
J that a curtain before the screen adds largely to the 
“tone” of the performance. This is especially true in 
theatres where the screen is on a stage, or is located in a 
cove-like structure. 

VALLEN AUTOMATIC CURTAIN MACHINE.— There is 
now on the market a device known as the Vallen Automatic 
Curtain Machine, illustrated in Fig. 364. This machine is very 
simple. It consists of a motor connected to a . cable drum by 
suitable gearing. The machine once started is automatic in 
its action, and its controlling switch may be located either 



Figure 364. 







874 


HANDBOOK OF PROJECTION FOR 


in the projection room, or elsewhere, or may be controlled 
from two different points. 

This forms an ideal installation, because with the switch 
conveniently located in the projection room, where it may be 
reached from working position beside either projector, tne 
projectionist can close the curtain machine switch and start 
his projector at the same time, whereupon the title of the 
picture is projected on the curtain, and is gradually revealed 
on the screen as the curtains are pulled away, or as the 
curtain is raised by the machine, as the case may be. 

In Fig. 365 we have a diagrammatic representation of the 
device, its location, and the cable arrangement and connec¬ 
tions with the curtain. The machine may either raise and 
lower the curtain, pull curtains sidewise, as per diagram, or 
it may loop them up and back them away from the screen. 
The practice in many of our best theatres is to suspend cloth 
curtains down over the screen from above, and to disclose 
the screen by draping or looping them back sidewise. 



Ditail anowiNO m [t non or Install.no 
T ill Vallin Automatic Curtain Machinl' 


u« t.J Vallkm Cito Co 
Aa«o* O. 


Figure 365. 






























































































































MANAGERS AND PROJECTIONISTS 


875 


When the curtains are to be pulled sideways they are 
suspended from and attached to cables I-I, Fig. 365, which, 
it will be seen by examining the arrangement, travel horizon¬ 
tally and in opposite directions above the screen, so that 
when the drum is running in one direction the left hand 
curtain will be pulled to the left, and the right hand curtain 
to the right, the direction of the curtains being reversed 
with the reversal of direction of motion of the drum. 

The practice pursued in many of the best theatres is to 
loop the curtains back. This is accomplished by using only 
one cable and branching it, attaching one branch to the front 
edge of each curtain, down far enough so that when the 
cable is pulled back the curtains will clear the screen. In this 
plan the opper end of the curtains is not attached to the 
cable, but to the walls or to some rigid support, so that the 
curtains are not separated at the top. 

The motor of the Vallen machine is specially designed, 
over size motor, built by the Robbins and Myers Company. 
Its starting, stopping and reversing is accomplished by means 
of an automatic switch and a mechanism designed specially 
for the purpose. Where the control is from the projection 
room, which is the plan we would strongly recommend, a 
four pole, double-throw, manually operated switch is located 
therein, in a position to be reached from working position 
beside either projector. Closing this switch in one position 
will start the curtain machine, after which it requires no 
further attention, as it will continue to operate until the cur¬ 
tains have reached the limit of their travel, whereupon the 
machine will automatically stop. When ready for the next 
operation it is only necessary to close the switch in the 
opposite direction. To open the curtains the switch is closed 
in one direction, and to close them the switch is closed in the 
other direction. That is all there is to it. 

The opposite end of shaft A, Fig. 364, is threaded, and upon it 
rides travelling head B, which same constitutes the controlling 
element of the machine. Collars C-D are adjustable on rod 
G, which, in turn, operates part E, which in its turn operates 
an automatic switch located inside box F. It will thus be seen 
that when travelling head B comes in contact with collar C 
or D, it will move rod G, and thus, through the movement of 
part E, open the automatic switch and stop the machine. The 
time the motor will run will depend upon the position of 
collars C and D, therefore, within the limits of the machine, 
merely by changing the adjustment of collars C and D, it may 
be made to pull the curtain or curtains any desired distance. 


876 


HANDBOOK OF PROJECTION FOR 


Besides the automatic controlling switch F, is an externally 
operated fused switch, designed to protect the motor. This 
switch does not show in Fig. 364, but is indicated at F in the 
diagram, Fig. 365. The threaded shaft by which the travelling 
head is controlled is so constructed that in case either one of 
collars C or D should become loose, the motor will continue 
to operate until travelling head B reaches the end of the 
threads, whereupon it will stand idle. This prevents possibil¬ 
ity of damage to the machine. Also by means of a mechanical 
safety clutch, described further along, no damage will be 
done to the curtain. 

On the inside of box F there is a safety arm, which is 
securely connected with travelling head B, so that in case 
the automatic switch for any reason does not work at the 
proper time, an instant later the safety arm throws the 
switch to open position, and stops the motor, which same 
cannot be again started until the cause of the trouble is 
removed. 

We therefore see that the machine is pretty well fool¬ 
proof, as well as very thoroughly automatic, and while we 
have not actually examined the device, the photograph in¬ 
dicates a rugged and excellent form of construction. 

The bearings of the motor are of bronze. Some of them 
have an oil well and are lubricated by means of oil rings, as 
per Fig. 148, page 448, while others are lubricated by means 
of a wick system. These latter have an oil cup on top of the 
bearing. The chain is a roller chain, the same as those used 
on motorcycles. The grooves on the drum are worm grooves, 
which insures the cable winding properly. 

MECHANICAL CLUTCH.— The drum is fastened to the 
shaft, which sprocket H is not, but idles thereon. On the inside 
of sprocket H is a mechanical clutch, with an adjustment screw, 
I, Fig. 364, extending from the end of the shaft on which the 
sprocket runs. By means of adjustment I, sprocket H can be 
made to move the drum when it is pulling any desired load. 
The object of the clutch is protection, both to the curtain and 
to the electrical part of the machine. In case the cables should 
get caught, or in case collars C and D worked loose and 
travelling head B was thus allowed to go too far, instead of 
tearing the curtain or stalling the motor, mechanical clutch H 
will slip, thus allowing the motor to run without operating 
the drum. 

The base and all the bearings supports are of cast iron, but 
the drum is aluminum. Travelling head B is of semi-steel, and 


MANAGERS AND PROJECTIONISTS 


8 77 


the switching mechanism of bronze. All parts of the machine 
are interchangeable, and every machine is guaranteed indef¬ 
initely against structural defect, so that any fault due to 
defective material or workmanship will be replaced without 
charge. 

OPERATING DIRECTIONS. —Each bearing support for the 
drum has one oil cup, the bearing for the gear two oil cups, 
and each motor bearing one oil cup. A few drops of the same 
oil you use on you projector (if you use good oil) in each of 
the bearings once a month, and a few drops on the threaded 
shaft and the roller chain once a month is sufficient. 

To locate trouble in case the motor will not run, it is 
necessary to: 

(A) See that the main line switch is closed. 

(B) Test the fuses. 

(C) Inspect for loose electrical connections in box F, 
Fig. 364. 

(D) See that the projection room controlling switch is 
making proper contact. 

(E) Open box F, Fig. 364, and see if the safety arm has 
thrown the switch to “open” position. If so, the spring has 
either become disconnected or is broken. 

Collars C and D, Fig. 364 are adjustable. Moving them away 
from the travelling head causes the curtain to travel a greater 
distance, and moving them toward the travelling head causes 
the curtain to travel a shorter distance. For instance, if the 
curtain is not completely closed, start the machine and allow 
it to operate in the direction of closing the curtain. If it stops 
automatically when the curtain is not quite closed, the button 
which is then nearest the travelling head should be moved 
away from the travelling head, not more than one-sixteenth of 
an inch. Having made this adjustment, let the machine again 
open the curtains and close them. If it does not quite close 
this time, move the collar a trifle more. To cause the curtains to 
open farther, the same operation is necessary at the other end 
of the travelling head. When the curtains are open the button 
nearest the travelling head must be moved a bit further away, 
if it is desired to have the curtain open wider, or it must be 
moved toward the head if the curtains opens too much. One 
eighth of an inch movement of collars C-D represents an 
eight inch change in the travel of the curtain. 

SLIPPING CLUTCH.— To locate the cause of the clutch 
slipping: 

(A) Main line switch should be opened. 


878 


HANDBOOK OF PROJECTION FOR 


(B) All cables, pulleys and the curtain should be exam¬ 
ined, to make sure nothing has become fouled. After locating 
the trouble and repairing same, close the main line switch and 
start the machine to make sure everything is all right. 

Should the mechanical clutch slip under the load the ma¬ 
chine is pulling, turn adjusting screw I to the right one- 
quarter of a turn at a time until the slipping stops. 

CAUTION. —The adjustment of the mechanical clutch is 
important. Screw I must be so adjusted that the clutch will 
just pull the normal load the machine is called upon to 
handle. The clutch is a safety device and must not be tight 
enough to pull anything more than its normal load. If the 
curtain does not open and close completely, do not adjust the 
clutch differently, but locate the cause that has made it slip. 


MANAGERS AND PROJECTIONISTS 


879 


Projectionist’s Report 

I MPORTANT.—Every exhibitor should require his projec¬ 
tionist to make written report, on a proper blank form, of 
the condition of all films received from the exchange, or 
from another theatre, if the service is on circuit. 

Such report would entail some work, but the projectionist 
should, for his own protection, be willing to make it up. It 
should include a statement of the general condition of each 
subject and the number of mechanical faults found therein. 

The report should be made in duplicate, one copy retained 
in the? theatre files and the other forwarded to the exchange 
MANAGER. 

These two things constitute the value of the report, be¬ 
cause with such reports available in the theatre files, the ex¬ 
hibitor is able and ought to make complimentary comment 
on the condition of the film if the condition deserves it, when 
paying the film rental bill. On the other hand, if the condition 
of films is deserving of criticism it is the duty of the exhibitor 
to make emphatic comment on that fact, .and to send an em¬ 
phatic protest when he sends his check for service. 

If this procedure is followed by enough theatres, there can 
be no question as to its beneficial effect. The exhibitor should 
remember that the better the condition of the film, the better 
show will be placed on the screen. It is perhaps unnecessary 
to further remark that the better the show, the greater will 
be the patronage of his theatre. 

AN OUTRAGE.— The exhibitor should also remember that 
when he buys service (except in cases where the service is 
“on circuit”) he is paying for films in perfect mechanical con¬ 
dition, other than such defects as may naturally be expected 
if the films have been used for a considerable time. These 
latter defects include rain, the possibility of worn or strained 
sprocket holes and missing sections of film. 

They most emphatically do not. however, include mis- 
frarres, loose splices, torn film or broken sprocket holes. 

The exchange which sends out films in any other than per¬ 
fect physical condition, is so far as concerns splices, absence 


880 


HANDBOOK OF PROJECTION FOR 


of misframes, torn film and torn sprocket holes, is not keep¬ 
ing its contract with the exhibitor. 

The exchange which does these things is working an out¬ 
rage on both the exhibitor and the projectionist. It is not liv¬ 
ing up to the true meaning of its contract with the exhibitor 
and is forcing or attempting to force the projectionist to per¬ 
form its inspection and repair duties without pay. 

The author of this work is most emphatically of the opinion 
that it is a legitimate and important function of projection¬ 
ists’ unions to take up the matter of films received by their 
members in other than perfect physical condition, in so far 
as applies to splices, torn sprocket holes, torn film and mis¬ 
frames, and to take such steps as may be necessary to force 
reform. 

To attempt to project films containing loose splices, torn 
sprocket holes or torn films is dangerous. To project films 
containing misframes discredits the work of the individual 
projectionist, and through him discredits the organization to 
which he belongs. It is no part or parcel of his duty as pro¬ 
jectionist to make repairs which are presumed to be made by 
the exchange, and which the exhibitor is paying to have made 
by the exchange. 

We would suggest the following as in the nature of a good 
report though it may be changed to suit the individual idea, 
provided the points named be covered: 

PROJECTIONIST’S REPORT 

Date . 

Film received from. 

Name of Subject . 

No. and kind of faults found therein . 


Were films rewound before being shipped away? 
Inherent faults in the film, if any....'. 


Remarks 


, Projectionist. 


















MANAGERS AND PROJECTIONISTS 


881 


Warning 

T HOSE contemplating the erection of theatres or the re¬ 
modeling of an old one, should not leave the matter of the 
location or planning of the projection room entirely to 
the architect. There should be a stipulation in the agreement 
requiring the architect to consult with and be guided by the 
advice of a competent projection engineer in so far as con¬ 
cerns the projection room location and its planning. It would 
also be well if a competent projection engineer be called into 
consultation with regard to the screen, its immediate 
surroundings and the lighting of the orchestra pit. 

No matter how thoroughly competent an architect may be 
as to the planning of theatres, it by no means follows that he 
has competent knowledge of the requirements of either the¬ 
oretical or practical projection. 

As a matter of fact some of the very best architects in the 
country, including those who have planned some of the finest 
Broadway motion picture theatres, have perpetrated the most 
atrocious, outrageous blunders imaginable in projection room 
location and planning, and these blunders have operated to 
forever injure and deteriorate the screen results in those the¬ 
atres, and thus decreased their drawing power. 

Except in isolated cases it also is poor practice to allow the 
projectionist a free hand in projection room location and con¬ 
struction ; also, except in the case of men with wide experi¬ 
ence, the projectionist should not be allowed a free hand in 
the selecting of projection room equipment, because but rel¬ 
atively few projectionists have complete knowledge of the 
various problems involved in the location and the planning of 
the projection room, and except in the case of projectionists 
of wide experience, who have made a real study of their pro¬ 
fession the projectionist is likely to be prejudiced in favor 
of the equipment with which he is most familiar, and unable 
to make a really intelligent comparison of the merits and de¬ 
merits of the various types of equipment on the market. 

It must be remembered that, while the projectionist may 
be a very competent man in so far as his knowledge of 
theoretical and practical projection be concerned, still, un¬ 
less his experience has been very wide indeed, it is hardly 


882 


HANDBOOK OF PROJECTION FOR 


possible that he can be sufficiently familiar with all the var¬ 
ious kinds and types of equipment used in projection work 
to be able to select the best there is to be had. It also must 
be remembered that neither the manufacturer or his engineer 
can be depended upon to say that the goods of a rival man¬ 
ufacturer are best. They have goods to sell and their business 
is to sell them. They may honestly believe theirs to be the 
best equipment, but in the very nature of things they are 
prejudiced and hardly able to make an unbiased comparison. 

There are now available a few really competent projection 
engineers who have no “ax to grind” in the matter of equip¬ 
ment. These men should be consulted. Not only should they 
be asked what equipment is best, but the exhibitor should 
insist that the engineer make clear the reasons why the 
equipment he names is best. 

In the matter of projection room planning and location, the 
foremost professional projector manufacturers have available 
a technical engineer who is entirely capable of giving com¬ 
petent advice. We would suggest that the exhibitor decide 
upon the kind of projector he is going to install, even before 
he plans the theatre, and then oblige his architect to consult 
with and be guided by the technical engineer of the projector 
manufacturer he proposes buying from in the matter of pro¬ 
jection room location and plans. 

The author of this book also is willing to act in an advisory 
capacity with regard to projection room location and plans. 
In his case, however, there is a charge for the service, and 
while this charge is quite reasonable, the services of the pro¬ 
jector manufacturer’s technical engineer may be had free of 
cost. 

Remember that the box office income of the theatre will be 
injured by anything that injures screen results. It is therefore 
not good policy to place high-class screen results at the 
mercy of an architect who, however learned he may be along 
general construction and decorative lines, knows little or 
nothing about practical projection, and probably not over¬ 
much about the technics of projection. Such a course cannot 
but result in the hampering of the work of the projectionist, 
and the injury, to a greater or less extent, of the results on 
the screen. 

Consulting a competent projection engineer in matters of 
this kind will save you money in the end, even though it is 
necessary to pay a fee for his services. The return should be, 
and in all human probability will be, at least a hundredfold. 


MANAGERS AND PROJECTIONISTS 


883 


Projectionist’s License 

I N the past there has been considerable opposition on the 
part of theatre managers and exhibitors to projectionist 
license laws. Also there has been opposition on the part 
of the I. A. as an international to the enactment of license 
laws, though many local unions have worked for and secured 
them. 

The author of this book is on record as favoring the enact¬ 
ment of license laws, even though there be a fee attached 
thereto, although any fee other than one sufficient to cover 
the actual cost of the operation of the law is- unquestionably 
wrong from any and every viewpoint. Society has the right 
to protect itself against the incompetent, but it has not the 
right to charge a man for the privilege of working at his 
chosen calling, and any fee over and above that necessary to 
pay the cost of operating the law would amount to exactly 
that. 

The benefit of the license law is made evident in the fact 
that, at least to some extent, it operates to curtail the supply 
of incompetent projectionists. 

It is, however, foolish to suppose that the mere existence of 
a license law will create competent projectionists. That can 
only be done by the proper administration of a well framed 
law, and the principal part of the administration is the hold¬ 
ing of an examination which can only be passed by men who 
really understand both the practical and technical end of 
their profession. 

Given the best law in the world, and an examining board 
from which licenses can be bought, or an examining board 
which plays favorites in an examination, or an examining 
board the members of which themselves lack the knowledge 
necessary to conduct a really competent examination, and the 
law is very largely made of no effect. On the other hand, 
given a proper law and an honest, competent examining 
board, great good will be accomplished both to the profession 
and to the industry as a whole, or, perhaps we might better 
say, to all concerned, 


884 


HANDBOOK OF PROJECTION FOR 


A SERIOUS ERROR. —One fundamental error found in 
most examinations is that the examiners seem to recognize 
only one danger to the public, and that is the danger of fire. 
The truth of the matter is that with modern projection room 
construction, and the fact that the public now very generally 
understands that it is in no real danger from a projection 
room fire, the fire danger lacks considerable of being of as 
much importance as is danger of injury to the eye-sight 
through eye-strain. 

There is no more eye-strain in a properly projected mov¬ 
ing picture, projected under proper conditions of auditorium 
lighting, than there is in reading this printed page in good 
light, but if the projection be unintelligently done, or if the 
auditorium lighting be wrong, there may be very serious eye- 
strain. It is therefore of very great importance that the 
examination include a really competent investigation of the 
knowledge of the projectionist as applies to the optics of 
projection. 

It is quite true that fire danger was what first brought about 
the licensing of projectionists. It is also quite true that at* 
that time danger to the audience from film fire was a real one 
because projection rooms were not then thoroughly fire¬ 
proof. Also in that day newspapers went to great lengths in 
what seemed an endeavor to impress the public the danger 
to audiences from film-fire, which action on their part was 
very largely responsible for the causing of wild panic the 
instant a projection room fire became visible to the audience. 

Improvement in both projection machinery and projection 
room construction and the education of the public to the fact 
that there is little or no danger to them from a projection 
room fire has changed all this, whereas increased brilliancy 
of projected light and other things have made the item of eye- 
strain, set up by improper procedure, of very greatly increas¬ 
ed importance. It is therefore rather absurd to hold an ex¬ 
amination covering only electrics when optics is in many 
ways now the more important. 

The licensing power ought also to be deeply interested in 
the knowledge of the projectionist as to auditorium lighting, 
since not only may the value of what the audience pays its 
money to see be greatly lessened by improper lighting of the 
auditorium, but mistakes in lighting of the auditorium while 
the picture is on may operate to set up literally tremendous 
eye-strain to the audience, or to portions of the same. 

Only the competent man will be able to keep the projector 


MANAGERS AND PROJECTIONISTS 


885 


in such adjustment and in such repair that there will be a 
minimum of movement in the picture on the screen. Also, 
only the competent projectionist who is thoroughly conver¬ 
sant with the optics of projection in all that subject entails, 
can so adjust and trim his revolving shutter that it will meet 
the local condition, and thus enable the projection of 
pictures at proper speed without flicker. Also, only the com¬ 
petent projectionist can so select and adjust the optical sys¬ 
tem of the projector that there will be no unnecessary waste 
in electric energy, and wasted electric energy not only means 
unnecessarily excessive bills for current, but also a waste of 
the diminishing fuel resources of the country. True, this latter 
might amount to very little in one theatre, but if there be a 
waste of even so little as 500 watts (it will probably average 
considerably more than this) in each theatre, when we mul¬ 
tiply 500 watts by the 16,000 theatres in the country, the ag¬ 
gregate of waste becomes 8,000,000 watts of energy, charge¬ 
able directly to incompetency, and 8,000,000 watts or 8,000 
kilowatts is no small matter when we reduce it to terms 
of coal, or when we add its costs to the overhead of the in¬ 
dustry. It is close to 2,000 horsepower, and at 8 cents per 
kilowatt hour would amount to $3,200 per day, if all theatres 
ran an average of five hours a day, or a total of $1,168,000 a 
year added to the overhead of the industry. 

NEWSPAPERS AND FIRE DANGER.— Let us for a 

moment direct attention to the responsibility resting upon 
the newspaper editors of this country, who permit the publi¬ 
cation of ridiculous stories about fire danger as applies to 
the motion picture theatre. 

Newspaper editors should inform their readers that in 
modern motion picture theatres the projection room is abso¬ 
lutely fireproof, and that a film fire therein entails abso¬ 
lutely no danger of any kind whatsoever to the audience, 
except possibly the unpleasant experience of breathing a 
little smoke, always provided the audience leaves the theatre 
decently and in order. In modern motion picture theatres 
absolutely the only danger to the audiences from film fires 
is summed up in one word—“PANIC.” 

We make the broad assertion that newspaper editors them¬ 
selves are very largely responsible for all injury and death 
resulting from motion picture theatre fire panics through 
their failure to inform their readers of the facts in the case. 

We do not wish to be understood as intimating that the 
projectionist should not be thoroughly examined as to his 


886 


HANDBOOK OF PROJECTION FOR 


ability in electrics and along the lines of fire hazard. Aside 
from danger to the audience, a projectionist is placed in 
charge of valuable property within the projection room, 
which may be either seriously damaged or even entirely de¬ 
stroyed by fire. It is, therefore, right and proper that he be 
examined along these lines, but that should be only a part of 
the examination. 

In connection with these things it must, of course, be 
admitted that the projectionist who is thoroughly competent 
so far as technical knowledge goes, may be in fact thoroughly 
incompetent because he is too shiftless or lazy to apply 
his knowledge. The fact remains, however, that the mart 
who is competent in technical knowledge can be compelled to 
do his work right, whereas the man who does not possess 
technical knowledge cannot be compelled to do his work 
right because he does not know how. 

INCREASES EFFICIENCY.— The licensing of projection¬ 
ists, even if the examination is not what it ought to be, tends 
to increase efficiency, because knowing they must pass an 
examination the candidates will do at least some studying, 
and the knowledge thus acquired they would not in all human 
probability otherwise possess. 

The exhibitor, and the theatre manager who is a real 
manager, will not oppose anything tending to increase the 
efficiency of projectionists, because it is upon that efficiency 
he must depend, not only for results on the screen, but also 
for the securing of those results without excessive cost. 

The author is heartily, thoroughly and completely in ac¬ 
cord with the licensing and examination of projectionists. He 
suggests, however, that it is essential to good results that the 
examining board be either wholly or partly composed of men 
who have at least a fair working knowledge of practical 
projection. 

The fact that a man occupies a position as head of a city 
department or state department is absolutely no proof that 
he is a competent examiner for moving picture projectionists, 
any more than he would necessarily be a competent examiner 
for locomotive engineers or sea captains; also, the fact that 
a man is a competent electrician does not qualify him to ex¬ 
amine projectionists, except in so far as their knowledge of 
electricity is concerned, which latter is but a relatively small 
part of the knowledge necessary to competency 


MANAGERS AND PROJECTIONISTS ' 887 


COMPOSITION OF EXAMINING BOARD.— It is hard to 
say just what the make-up of an examining board should be. 
The following is perhaps as near the composition of a com¬ 
petent examining board as it would be possible, everything 
considered, to get: (a) One thoroughly competent, practical 
electrician; (b) the head of building or fire inspection de¬ 
partment; (c) one man who is thoroughly acquainted with 
practical projection room practice—in other words, a com¬ 
petent projectionist. 

THE EXAMINATION.— The examination of projectionists 
should seek to determine: (a) Their knowledge of electrical 
action in general; (b) their knowledge of electrical action as 
applies to the ordinary multiple arc and three-wire system— 
particularly the latter; (c) ability to measure wires, to calcu¬ 
late their ampere capacity and their general understanding of 
what various things happen, or may happen, when a wire is 
overloaded, and why they happen; (d) their knowledge of 
what types of installation (wiring, etc.) are permitted for use 
under various conditions met with in the theatre; (e) extent 
of their knowledge of the principles involved in trans¬ 
formers, and of the construction, connecting and operation of 
low voltage transformers or economizers such as are used in 
projection rooms; their knowledge of motors and motor 
generators, particularly as applies to the care of the commu¬ 
tator, brush tension, methods of fitting the brushes to the 
commutator and testing for possible electrical faults; (g) 
knowledge of the principles involved in, and the practical 
operation of the mercury arc rectifier, if they are used in the 
territory; (h) knowledge of principles involved in fusing, 
including knowledge of all places where fuses are required, 
and what types of fuses it is permissible to use in a theatre; 
(i) knowledge of rheostat resistance and its application to 
the projection circuit; (j) Knowledge necessary to determine 
whether or not wires are large enough to carry any given 
current, considering length of circuit; (k) knowledge of the 
various points in projection room construction and equip¬ 
ment, including proper methods of port fire shutter sus¬ 
pension, fusing port fire shutter suspension system, par¬ 
ticularly as applies to location of fuses, and method of manual 
operation of same; (1) knowledge of the projection mech¬ 
anism and of the light source; (m) knowledge of film, in¬ 
cluding how to make a proper, straight, smooth splice, the 
effect of worn sprocket teeth on the film and on the projected 
picture; the effect of worn aperture plate tracks on screen 


888 


HANDBOOK OF PROJECTION FOR 


results; (n) knowledge of optical principles involved in the 
revolving shutter of the projector, including how to make a 
shutter fit local conditions as nearly as it can be made to do 
so; (o) knowledge of proper storage of films in the projec¬ 
tion room; (p) knowledge of proper projection room lighting 
and its effect on projection; (q) knowledge of screen surfaces 
and their effect in auditoriums of different dimensions; (r) 
knowledge of proper picture size under various conditions, 
the effect of seats being placed too close to the screen; (s) 
knowledge of how to measure focal length of lenses; (t) 
knowledge of proper selection of and adjustment of the 
various elements of the projector optical system, and 
such other things as may occur to the examiners, not over¬ 
looking the cause of damage to film in re-winding and how 
to minimize it, and the various effects of overspeeding pro¬ 
jection. 

COMPETENT EXAMINERS.— Up to date what is perhaps 
the worst trouble in the whole licensing proposition is that 
very few examiners are themselves equipped with the knowl¬ 
edge necessary to conduct a really competent examination. 
Also, few examining boards are supplied with the equipment 
necessary to the conduct of a competent examination. We 
might add that the issuance of licenses except to men who 
have successfully passed a really competent examination 
savors of dishonesty to the public; moreover, it savors of 
highway robbery to compel a projectionist to pay a fee for a 
license which is issued as the result of an examination having 
little or no practical value. 

ROUGH DRAFT OF LICENSE LAW.— It would be im¬ 
practical to include a model law in this book, because of the 
difficulty in framing one which would, in all its details, be 
applicable to varying local conditions. Fundamentally such 
a law should be the same in any locality, and the fundamental 
principles involved I shall set forth, leaving the necessary 
details to be worked out to fit individual local needs. 

(1) Designate places in which it shall be illegal to display 
motion picture films until the projection apparatus and the 
projection room have been approved and duly licensed. 
Name the licensing power and give it authority to make 
necessary rules and regulations and to enforce them. 

(2) Provide for an examining board, for the necessary 
equipment and for the examination. Specify briefly the 
qualifications necessary to obtain such license, which must 
include a competent knowledge of projection optics, the pro- 


MANAGERS AND PROJECTIONISTS 


889 


jector optical system, electrics and electric appliances as ap¬ 
plied to projection work, fire hazard and local laws which 
apply to projection work. Require that the applicant for 
license shall have a certain amount of experience, either as 
a projectionist or projectionist’s assistant to be eligible for 
examination. Establish a minimum age of a projectionist, 
which in no event should be less than nineteen years. As a 
matter of fact, twenty-one should be the minimum. 

(3) Provide for the licensing of persons to act as assistant 
to projectionist, and designate what work they may do in 
the projection room, and what they shall not do, one item of 
which is that they must not project pictures until a stated 
period of not less than one-half on the total time of ap¬ 
prenticeship has passed, and then only when a licensed 
projectionist is present in the room; minimum age to be the 
requirement for a projectionist less the time of apprentice¬ 
ship required by law. 

(4) Provide for fees to be paid for the licensing of pro¬ 
jectionist and assistant; also for annual renewal of the two 
last mentioned licenses, and fee for the same. These fees 
should be only sufficient to bear actual cost of operation of 
the law. 

(5) Provide penalties for violation of any provision of law, 
or any rule or regulation made by the licensing authority. 

(6) Provide that license MAY (not shall) be renewed at 
expiration without re-examination, provided application be 
made within a stated period, not exceeding thirty days, after 
such expiration. 

In addition to these general provisions we would suggest 
that the law governing projection rooms should make pro¬ 
vision for (a) their thorough ventilation; (b) a vent flue 
sufficiently large to carry away all fumes and smoke in case 
of film fire, same to contain an electric exhaust fan of ample 
dimensions; (c) a fire shutter fusible link system along the 
lines suggested on Page 314, (d) forbid placing conduit 
on the floor surface; (e) that the projection room con¬ 
struction be such that its walls will be thoroughly fireproof, 
and that either brick, hollow tile, or concrete be required 
where its use is practical; (f) that the projection room feed 
wires be large enough to carry the combined current capacity 
of all apparatus in the projection room, regardless of whether 
it is ever all used at one time or not; (g) that the wiring be 
so done that the projectionist will, in case of need, be able 
instantly to switch on at least a portion of the auditorium 


890 


HANDBOOK OF PROJECTION FOR 


lights; (h) that a metal receptacle for hot carbon butts be 
required; (i) that all film rewinding and repairing be done 
either inside the projection room or in a fireproof room 
immediately adjoining and connecting thereto; (j) that a 
proper fireproof metal receptacle, containing a separate fire¬ 
proof compartment for each film, be required for film storage, 
and that it be required that all film not in actual use, in 
process of repair, or rewinding be at all times kept in their 
receptacle; (k) that metal lining of projection rooms be for¬ 
bidden; (1) that the projectors be thoroughly grounded to 
the metal framework of the projection room, if such there 
be; (m) that the keeping of oils, alcohol or highly in¬ 
flammable substances in quantities of more than two ounces 
each be forbidden; (n) that no exposed inflammable ma¬ 
terial be allowed inside the projection room except a work¬ 
bench of two-inch hardwood lumber, and such hardwood 
shelving as may be required, all wood for such purposes to 
have first been soaked for forty-eight hours in a fire¬ 
proofing solution, see page 249; (o) that observation ports 
shall be not less than sixteen (16) inches wide, square or 
rectangular in form, and of such height as will provide a 
good view of the screen by a man of minimum and maximum 
height when seated or standing in working position beside 
the projector. See page 307. 


MANAGERS AND PROJECTIONISTS 


891 


Electric Meters 

T HE watt hour meter is the instrument now in general 
use for measuring the electric power consumed. The 
measurement is in watt hours, the meaning of which is 
that a certain number of watts have been used for a certain 
given number of hours, the use of one watt for one hour 
being the unit of measurement. The principle of operation 
of the electric meter is as follows: 

The dial which records the consumption of the power is 
operated by a specially constructed, very small motor, placed 
in series with the current consuming apparatus. The motor 
is so constructed that if it were operated at a pressure of 
one volt for a period of one hour, during all of which time 
one ampere of current flowed, it would record one watt, or, 
in other words, one watt hour. This means that if, for in¬ 
stance, the motor be run for one hour under a pressure of 
110 volts, with 10 amperes of current flowing, it would move 
the dial hand just far enough during that hour to record 
110 x 10 = 1,100 watt hours, or 1.1 kilowatt hours, or if the 
pressure be 110 volts and the amperage 100, then during the 
same time the motor would move the dial hands far enough 
to record 110 x 100 = 11,000 watt hours, or 11 kilowatt hours* 
This roughly describes the principle of operation upon 
which the electric meter is based, and in a work of this 
kind that is all that could be expected, because to give you a 
thorough detailed understanding of meters would consume 
a great deal of space, without commensurate benefit. 

TESTING METER. —If it is suspected the meter is wrong 
the instrument may be roughly tested in several ways, one 
of which would be to connect an ammeter into the lines and 
a volt meter across the lines near the meter. Read the 
meter and then burn a number of lamps for a period of 
exactly one hour, during which time the meter must record 
exactly the wattage obtained by multiplying the reading of 
the ammeter by the reading of the volt meter, both of which 
should first be tested to make sure that they are correct. This 
is not intended as a conclusive test, but if after making such 
a test there is a discrepancy between the meter and the 
wattage indicated by the volt meter and ammeter, then you 


892 


HANDBOOK OF PROJECTION FOR 


should insist upon the power company making a regular test 
of the meter. In making such a test, however, it is im¬ 
perative that the voltage and the amperage remain abso¬ 
lutely constant during the entire period of the test. 

READING THE METER. —An electric meter is read pre¬ 
cisely the same as is the gas meter. First carefully note the 
unit at which the dials are read. On all meters used by the 
Edison Company the figures above or below indicate the 
value of one complete revolution of the pointer, hence one 
division indicates 1/10 of the value of the complete revolu¬ 
tion of the dial hand. Carefully note the direction of rota¬ 
tion of the dial hand, as indicated by the figures, the pointers 
moving, of course, from 0 to 1, 2, 3, 4, etc. Each dial will 
read in an opposite direction to its neighbor. 

Counting from right to left on a five-dial register the 
pointers of the first, third and fifth dials of a watt hour 
meter rotate in the direction of the hands of a watch, or to 
the right, while the hands of the second and fourth move 
in the opposite direction, or counter-clockwise. The same 
holds true of the four-dial register. The hands of the first 
and third dials move to the right and the second and fourth 
to the left. The dials must always be read from right to left, 
and the figures set down as read, remembering that until 



Figure 366. 







MANAGERS AND PROJECTIONISTS 


893 


the hand has reached a division that division must not be 
counted. For instance: In No. 3, Fig. 366, the right-hand 
dial has passed 1, but has not yet reached 2, therefore it 
reads 1. Likewise the second or 100 dial hand has passed 2, 
but has not reached 3, hence it reads 2. Taking No. 1, Fig. 
366, for example, it reads as follows: A complete revolution 
of the right-hand dial would be 1,000 watt hours, but the 
pointer has just reached the figure 1, which, being 1/10 
of 1,000 is 100. We therefore put down 100. The next dial 
stands at 1, which, since one division is 1/10 of the total 
of 10,000, equals 1,000. Therefore we set down 1 at the left 
of the 100, and have 1,100. The next dial also stands at 1, 
which being 1/10 of 100,000, is 10,000, so we set down an¬ 
other 1 at the left of 1,100, and have as a total 11,100. The 
next dial stands at 1, so we set down another 1 to the left, 
and as a result have 111,100. The last dial stands at 1, 
which calls for still another 1 at the left, and we have a final 
reading of 1,111,100 watt-hours. No. 3, Fig. 366, reads in 

k. w. hours. It is read the same as is No. 1. The right-hand 
dial registers up to 10 k. w. h. The pointer is passed 1, but 
has not yet reached 2, therefore we put down 1, that being 
1/10 of the total of 10. The pointer of the next dial has 
passed the 2, but has not yet reached 3, therefore we puJ 
down a 2 to the left of 1. The pointer of the third dial 
reads 1, and that of the fourth 9, therefore we have a total 
reading of 9,121 k. w. h. In No. 2, Fig. 366, the pointer stands 
at 9, which would mean 900 watts. The next three dials 
stand at 0, therefore we precede 900 with three 000’s, thus 
000,900. The pointer of the last, or 10,000,000 dial, stands at 

l, so that the reading would be 1,000,900 watt-hours. The 
reading of No. 4 would be 1,097 kilowatt hours. 

CAUTION.— Some meters read as per their dial indication. 
Other meters are not direct reading, but require that the 
actual reading shown by the dials be multiplied by a con¬ 
stant in order to obtain the correct reading. This is for the 
purpose of keeping meters of various capacities at fairly 
uniform size. If the constant were not used meters of larger 
capacity would be of greater dimensions than those of small 
capacity. If the register face bears the words “multiply 
by 3,” or any other number, then you must multiply the 
actual reading as indicated by the various dial faces accord¬ 
ingly. 

The theatre manager or the projectionist should always 
read the meter when the company man reads it, and make a 


894 


HANDBOOK OF PROJECTION FOR 


record of the reading in a book kept for that purpose. This 

is not only a goodly precaution, but it enables the compu¬ 
tation of the current consumption at any time it may be 
desired. For instance, when the man reads the meter, it 
registers 1,000 kilowatt hours, that being on the first of the 
month. On the 10th of the month you take another reading, 
and the difference between the two will indicate the energy 
consumed during that period. 


KNOWLEDGE IS POWER. 



MANAGERS AND PROJECTIONISTS 


895 


Bell Wiring 

T HE electric bell and annunciator play quite an impor¬ 
tant part in a theatre. The installation of a single 
bell is illustrated in Fig. 367. After installing the 
bell and the push-button in the location desired one wire is 
run directely from one side of the push-button to the bell. 
Another wire is run from the other side of the bell to one 



Figure 367. 


side (either one, it makes no difference) of the battery, and 
another wire is run from the other side of the battery to 
the other side of the push-button. This completes the in¬ 
stallation. For a single bell one battery alone or two bat¬ 
teries in series may be used. By series I mean two batteries, 
with the carbon of one battery connected to the zinc of the 
other battery by means of a short wire, as at A, Fig. 369. 
The effect of two batteries connected thus is to cause the bell 
to ring louder. 

The ordinary practice in moving picture theatres is to use 
either bells, buzzers, or small, low candle-power lamps for 
signaling to the projection room, piano player and the man¬ 
ager. Of the three, the lamp system, if properly installed, is 











896 HANDBOOK OF PROJECTION FOR 

the best, with the buzzer as second. The bell should never 
be used. A buzzer is merely an electric bell without the bell 
part. 

What is known commercially as the dry battery is best for 
theatre work. Wet batteries are very effective, and very 
cheap in operation, but they are liable to freze in winter and 
thus cause a lot of trouble. The dry battery is cheap and 
effective. 

For wiring bells No. 18 ordinary cotton covered bell wire is 



plenty good enough, unless the circuit be a very long one, in 
which case No. 16 might be used. This holds good, except in 
very wet places, where it is better to use rubber covered 
wires, supported upon porcelain insulators. 

In putting up bell wires they may be gathered together in a 
cable and held to the wall with a wooden cleat. They may 
be run singly around picture molding, being held thereto by 
small iron staples, but where this is done a staple should 
never be driven over two wires, since it is likely to cut 
through the insulation and short-circuit the bell, the battery 
or both. Never drive a staple over two wires. Hold each 
wire with its own staples. A short circuit may cause your 
bell to ring all the time or not ring at all, according to its 
location. If on the two wires leading to the push-button the 
bell will ring continuously until the battery is worn out. If 
on the wire running from bell to battery and the wire run¬ 
ning from button to bell the bell will not ring at all. Joints 
in the wire should be made in the usual way (see wire 























MANAGERS AND PROJECTIONISTS 


897 


splices, Page 123, and should be soldered and wrapped with 
insulating tape. Never run your wires in a slipshod manner. 
Always do a job in a workmanlike way. Stretch the wires 
tightly and run them as they should be run. Loose, sagging 
wires advertise the poor workman. 

A, Fig. 369, shows series connection of batteries, which 
has the effect of raising the pressure approximately one volt 
for each battery added. B shows multiple connection, which 
increases amperage, but not the voltage, and C a series- 
multiple connection which increases both volts and amperes. 

A very common practice in theatres is to use what is 
known as the three-wire system of bell wiring. This system 
is the most economical in that it requires a comparatively 
small amount of wire for the installation of several bells. By 
its use any number of bells may be run with one battery, 
and each bell has its own individual push-button. No push¬ 





button will ring any bell but its own. Put up the bells, buzz¬ 
ers, or lights, and the push-button wherever you wish them 
to be. Use two batteries, connecting the carbon of one to the 
zinc of the other. Get bell wire of three different colors. The 
installation is illustrated in Fig. 368, in which A-A-A are bells, 
B-B-B push-buttons, and C a two-cell dry battery. 

The reason for three colors is to avoid mistakes and con¬ 
fusion and to be able to find any particular wire anywhere 








898 


HANDBOOK OF PROJECTION FOR 


afterward, without tracing it clear from the battery or bell. 
The use of three colors of wire simplifies matters very 
greatly. Suppose you get red, blue and white. You take 
one color, say, the blue, and run it from one (either) binding 
post of the battery to one (either) binding post of each bell. 
You may run separate wires from the battery binding post 
to each bell or run one wire reaching all bells or you may 



branch off to a bell at any point. Next take another color 
(red, for instance), and run from the other battery binding 
post to one. (either) side of each push-button. You now 
have one side of the battery connected to one side of each 
bell and the other side of the battery connectd to one side 
of each push-button. You next, with the remaining color 
(white) wire, connect the remaining side of each push¬ 
button with the remaining side of the bell it is to ring, and 
the job is done. The blue wire (blue in this case) is called 
the common bell wire, the red wire is called the push-button 
wire and the whites are called the individual wires. It is 
these latter wires which determine which bell a button will 



Figure 371. 



























MANAGERS AND PROJECTIONISTS 


899 


ring and you may cause a button to ring a different bell by 
simply changing the individual wire to that bell. Fig. 368 
shows a plan of this system. 

An additional bell easily may be installed at any time as 
follows: Test the bell and install it and its push-button 
wherever you want them to be. Now with a piece of the first 
color wire connect one binding post of the bell with the first 
color wire already in use wherever you can find it. With a 
piece of second color wire connect one side of the push¬ 
button with a second color wire wherever you can find one. 
Understand you can just tap on to these wires at any point 
you can locate one of proper color. Now connect the re¬ 
maining side of the button with the remaining side of the 
bell with third color wire and the job is done. The rules 
governing this system of wiring are as follows : One side of 



the battery must be connected with one side of each bell by 
first color wire. The other side of the battery must be con¬ 
nected to one side of each push-button with second color 
wire and the remaining side of each button must be con¬ 
nected with the remaining side of the bell it is to ring with 
third color wire. . 

The various battery combinations are illustrated in Fig 
369. A increases the voltage without affecting the amperage 
B increases the amperage without affecting voltage. C in¬ 
creases amperage and voltage. A is series, B multiple and C 
is a multiple of series. 

In Fig. 370 we see two fire bells, one located, let us sup¬ 
pose, in the manager’s office, and the other on the stage, or 
at any other suitable point. We also see an ordinary push¬ 
button at A, and a form of contact more suitable to such 
work at B, either of which will ring both bells. As many of 
these may be attached as desired, locating them at any point 












































900 


HANDBOOK OF PROJECTION FOR 


in the house. Attach one side of the button to upper wire 
and the other side to the battery wire, as shown. In the 
illustration we see four batteries connected in series. This 
being a fire alarm system, it is desired that the bell or 
buzzers ring very loudly, hence several batteries are con¬ 
nected in series. Employees should be made to understand 
that it will mean instant dismissal to ring these bells, except 
in case of actual necessity. The system can be arranged for 
any number of bells, from one to a dozen, and there can be 
as many push-buttons as desired. 

Fig. 371 illustrates the method of connecting a bell so that 
it may be rung by more than one button. By this plan as 
many buttons may be installed as desired, any one of which 




will ring the bell, provided the wire from push-button to 
battery wire be not connected between battery and bell. 
A-A-A are push-buttons. 

In Fig. 372 we see the method of wiring an ordinary an¬ 
nunciator. The plan is too plainly shown to require explana¬ 
tion. The buttons may, of course, be located anywhere in 
the building, and ordinarily are widely separated. 

ELECTRIC PROGRAMME BOARD.— Fig. 373 is the 
wiring diagram of an electric programme board. I think the 
action will be plain when you trace through the contacts in 
Fig. 373. 

Wire A, we may call the permanent connection. As you 
will observe, it connects directly to one side of all the 
lamps. Wire B connects through switch C and movable 
arm D to the v-r : o"s contacts 1, 2, 3, 4. etc. Now suppose we 













































MANAGERS AND PROJECTIONISTS 


901 


place arm D on contact 1. ' You will observe that the current 
will flow through wire E, through lamp 1, and thence back 
through the other wire, and that no other lamp will be 
affected. If we move the arm to contact 6, then only lamp 6 
will be lighted. Such a board is simple, entirely practical, 
and, as we have said, is the best plan we have seen. It is 
also quite possible to substitute single pole, single throw 
knife switches for contacts 1, 2, 3, 4, etc., connecting wire B 
to one side of all these switches. The switches or the con¬ 
tacts should be located at the most convenient point, either 
on the stage, by the side of the musician or in the projection 
room. The transparency can be so made that only the figure 
or name actually illuminated will be visible. This may be 
done b}' covering the whole front of the board with ground 
glass, on which are the figures, or names blocked out in 



black, as shown in the illustration, each lamp, however, being 
contained in a light tight compartment of its own. Different 
colors ma}' be obtained, if desired, by covering the various 
characters with light shades of gelatine or using colored 
globes. 

In practice, we would by all means advise a double-pole 
single throw switch at AB, rather than the single-pole knife 
switch at C. In fact switch C would be a violation of Under¬ 
writers’ rules. 

In Fig. 374 a battery of 36 lamps is arranged in the form of 
a square, with 6 lamps either way. One wire (wire A, in the 
sketch) is connected directly to one side of each lamp. A 
board is now made, containing 36 sockets, arranged in a 
square, with 6 sockets each way, the same as are the lamps. 






































902 


HANDBOOK OF PROJECTION FOR 


This board may be placed in any convenient location, either 
near the lamps or removed at a distance from them, as may 
be most convenient; but in any event the other side of each 
one of the lamp sockets must be connected to one side of 
each socket as shown. We now c6nnect the other side of 
each one of these sockets to wire B, as shown in the illus¬ 
tration, installing a double-pole, single-throw switch, at any 
convenient point in wires A, B. Both sides of the socket are 
now alive, one directly from wire B and the other by way of 
the lamps through wire A. It will be readily seen that if an 
ordinary plug fuse be screwed into any one socket the lamp 
connected to that socket by cross wire will immediately be 
lighted and will burn until the plug is removed. Suppose we 
wish to form a figure 3. It would be only necessary to in¬ 
sert the plugs in the sockets indicated in order to outline the 
figure 3 on the board, wherever it might be placed. In using 
such a plug board it is advisable to have a pattern of the 
various figures and letters it is desired to use. Patterns may 
be made of cardboard. 

Where printed programmes are used it is quite possible to 
install such a board at the side of the stage, with the plug 
board and the switch controlling the supply wires located in 
the projection room, within convenient reach of the pro¬ 
jectionist. He can then plug in any desired number and 
illuminate the same by merely throwing in the switch, i. e.: 
Supposing he is running reel 2, the next being, of course, 
reel 3, which is described on the programme under that 
number. He prepares Fig. 3 by placing the plugs in position 
in the board, and as reel 2 is finished he throws in the switch, 
illuminating figure 3, thus allowing the audience to look at 
the programme while the next reel is being threaded or 
during the interval between the two reels. Where only on* 
number is to be used the board can be made very small, and 
it is not necessary to use more than two or three c. p. lamps, 
these being of the proper voltage, of course. Such a board 
can be used to decided advantage in many ways. The lamps, 
if used within the auditorium, should be frosted or else 
heavily colored. It is possible to so connect the various 
figures through batteries of switches that the plug arrange¬ 
ment is unnecessary. This is more costly, and the plug 
serves every purpose. It is quite possible to substitute 
single-pole, single-throw switches, or ordinary snap switches 
in place of the plugs. The arrangement shown in Fig. 374 is 
much the best for programme announcements. 

COLORING INCANDESCENT LAMPS Projectionists or 


MANAGERS AND PROJECTIONISTS 


903 


theatre managers who may desire to color incandescent 
globes may procure ready-made coloring liquid from any 
supply dealer. These liquids come in red, green, blue and 
amber. 

Colored incandescent globes will require re-dipping oc¬ 
casionally, because the heat of the globes gradually deteri¬ 
orates the color. Color is applied by the simple process of 
dipping the incandescent globe into the liquid, afterward 
allowing it to dry. 

The Eastman Kodak Company recommends the following 
formula as calculated to produce a very pleasing amber color, 
with the remark that other dye materials may be used when 
some other color is desired: 

4*4 ounces Sandarac (Powdered). 

Yi ounce Venice Turpentine. 

58 grains Metanil Yellow No. 1955. (National Aniline Co., 
Buffalo, N. Y.). 

y 2 fluid ounce Lavender Oil (Garden). 

26fluid ounces Denatured Alcohol. 


904 


HANDBOOK OF PROJECTION FOR 


Projectionists’ Library 

I T is not only desirable, but necessary that those pro¬ 
jectionists who wish to succeed have available such 
books for study and reference as deal with those various 
things it is necessary to know. We have given consider¬ 
able thought to the matter of what books are really 
necessary. To be of use a book must be written in such a 
way that the purchaser can understand it, and but com¬ 
paratively few projectionists are able to use or understand 
technical language, or any other than very simple dia¬ 
grammatic drawings. To most projectionists a performance 
curve diagram is just as intelligible as so much Greek. It 
is, therefore, all but useless to recommend to him books 
which do not explain things in very plain, simple language, 
and use simple, understandable drawings. 

The books we have selected are among the good ones; 
they cover the entire ground with at least very fair degree 
of completeness. 

We recommend to you the following: 

Optic Projection, by Simon Henry and Henry Phelps Gage, 
730 pages, well bound in cloth ; price, $5.00. 

The Hawkins Electrical Guides, ten volumes, with a total of 
3,366 pages, bound in limp imitation leather; plain, under¬ 
standable and complete. 

The Electric Motor, by Elmer E. Burns. 

Moving Pictures; How They Are Made and Worked. By 
Frederick A. Talbot; of no especial direct benefit to the pro¬ 
jectionist in his work, but will be of interest to him, es¬ 
pecially in those chapters where it is explained how the 
various “tricks” in photography are performed. 340 pages. 

The various proceedings of the Society of Motion Picture 
Engineers are recommended. They may be purchased from 
the secretary of the society. 

The Projection Department of Moving Picture World, 
which has been the leader in matters projectional for many 
years. 

As to projection itself, we know of no book, other than 
this one, which we could conscientiously recommend. We 
know of no other work which covers the ground even fairly 


MANAGERS AND PROJECTIONISTS 


905 


well. We do know of some books on the subject of pro¬ 
jection which are very much worse than useless, because 
they are wrong and misleading in many things. We, there¬ 
fore, caution you to be very careful when buying books 
■dealing with the projection of motion pictures. 


THIS BOOK IS TO STUDY—NO! 
TO LET LIE ON A SHELF. 



906 


HANDBOOK OF PROJECTION FOR 


Decimal Equivalents 

The following complete table of Decimal Equivalents from 
1/64 to 63/64 of an inch, by sixty-fourth steps, was compiled 


.015625 

.03125 

.046875 

.0625 

.078125 

.09375 

.109375 

.125 

.140625 

.15625 

.171875 

.1875 

.203125 

.21875 

.234375 

.25 

.265625 

.28125 

.296875 

.3125 

.328125 

.34375 

.359375 

.375 

.390625 

.40625 

.421875 

.4375 

.453125 

.46875 

.484375 

.5 


.515625 

.53125 

.546875 

.5625 

.578125 

.59375 

.609375 

.625 

.640625 

.65625 

.671875 

.6875 

.703125 

.71875 

.734375 

.75 

.765625 

.78125 

.796875 

.8125 

.828125 

.84375 

.859375 

.875 

.890625 

.90625 

.921875 

.9375 

.953125 

.96875 

.984375 


Figure 375. 
































































MANAGERS AND PROJECTIONISTS 


907 


by the Lake Sales Company, New York City. We present 
it believing it will be of considerable convenience to users of 
this book. We are indebted to the Lake Sales Company for 
permission to use it. 


CENTIGRADE AND FAHRENHEIT SCALES 


Centigrade 

Fahrenheit 

Centigrade 

Fahrenheit 

0 

32 

50 

*122 

5 

41 

55 

131 

10 

50 

60 

140 

15 

59 

65 

149 

20 

68 

70 

158 

25 

77 

75 

167 

30 

86 

80 

176 

35 

95 

85 

185 

38 

1004 

90 

194 

40 

104 

95 

203 

42 

107.6 

ioo 

212 

45 

113 




MELTING POINT 

OF MATERIALS 



Fahrenheit 


Fahrenheit 

Mercury . 

. —39 

Bronze . 

. 1,692 

Tin . 

. 442 

Silver . 

. 1873 

Bismuth . 

. 507 

Copper . 

. . 1,996 

Lead . 

617 

Gold . 

.. 2,016 

Zinc . 

. 773 

Cast Iron, Gray. . 

. . 2,786 

Antimony . 

. . . 1,150 

Steel . 

. 2,372 to 2,552 

Aluminum . 

, ... 1,157 




TABLE OF REFLECTION POWERS BY DIFFERENT SURFACES 

This table should be of value to those selecting theatre 
interior decorations. The percentages indicate the propor¬ 
tion of the total light falling upon the various surfaces which 
is reflected. 


Material Per cent. 

Polished silver.92 to 93 

Mirror silvered on back.. .82 to 88 

White blotting paper.82 

White cartridge paper.80 

Polished brass.70 t« 75 

Mirror backed with Amal¬ 
gam .70 

Ordinary foolscap paper...70 

Chrome-yellow paper.62 

Orange paper .50 

Yellow wall paper.40 

Yellow-painted wall.40 

Light pink paper.36 


Material Per cent. 

Yellow cardboard.30 

Light blue cardboard.25 

Brown cardboard.20 

Yellow painted wall, dirty..20 

Emerald green paper.IS 

Dark brown paper.13 

Vermilion paper.12 

Bluish green paper........12 

Cobalt blue paper.12 

Black paper. 5 

Ultramarine blue paper. . . 3.5 
Black velvet.4 


FRACTIONS— In the making of calculations it is often 
necessary to add, subtract, multiply or divide fractions, and 
not every one can remember how to do it. We, therefore, 
give you the rules. 


ADDITION— To add two fractions it is first necessary 
that each one represent the same value as to parts- ^ ou 


































908 


HANDBOOK OF PROJECTION FOR 


cannot add 4/5 and 1/3, but you could very easily add 12/15 
and 5/15, and 4/5 and 12/15 and 5/15 and 1/3 have identically 
the same value. Before addition we, therefore, must give 
both fractions the same part value, which in arithmetic is 
called reducing them to a common denominator. Any two 
fractions may be reduced to a common demoniator by mul¬ 
tiplying both factors of each fraction by the denominator of 
the other fraction, thus in adding 2/3 and 1/9 we would have 


2 

2x9 

18 1 

1x3 

3 

18 3 

21 

— 

=- 

= — and — 

=-= 

— 

and — + — 

= —, 

3 

3x9 

27 9 

9x3 

27 

27 27 

27 


SUBTRACTION.—To subtract two fractions we proceed 
the same as for addition, but subtract the smaller numerator 

18 3 15 

from the larger, thus: 2/3 — 1/9 =-= —. 

27 27 27 

MULTIPLICATION.—To multiply a fraction by a whole 
number you may either multiply the numerator or divide the 
denominator by the wh.ole number, as seems most expedient. 
The results will be the same, thus: 1/8 x 4 = 4/8 if we mul¬ 
tiply the numerator, or 1/2 if we divide the denominator. The 
result is the same, because 4/8 = 1/2. 

To multiply a fraction by a fraction we multiply the numera¬ 
tors together for a new numerator and the denominators to- 

3 2 3x6 6 

gether for a new denominator, thus — x — = - = —. 

11 7 11x7 77 

DIVISION—To divide a fraction by a whole number you 
may either divide the numerator or multiply the denominator 
by the whole number. The result will be the same in either 

8 8-M 

case, insofar as has to do with value, thus: — = 4 =-= 

9 9 

2 8 8 

— or-= —, the value of 2/9 and 8/36 being the same. 

9 9x4 36 

To divide a fraction by a fraction you merely invert the 
divisor and then proceed as in multiplying one fraction by an- 

2 5 2 7 2x7 14 

other, thus: — = — = — x — =-= —. 

3 7 3 5 3x5 15 





MANAGERS AND PROJECTIONISTS 


909 


rTIHIS book represents almost three years of hard 
I work, as well as the knowledge and experience 
gained in all the years before. I hope and believe it 
ivill meet with your approval. If it does I shall feel thank¬ 
ful that my effort has not been in vain. 

I ask that you look upon such errors as there may be 
with kindly tolerance, remembering that to create a work 
of this magnitude and character, covering a comparatively 
new field, without error, would be too much to expect , or 
even hope for. 

It is with a feeling of literally tremendous relief, as in 
the laying down of a heavy, long-borne burden, that I 
dedicate this work to the memory of my friend of other 
days, James P. Chalmers, and sign 










910 


HANDBOOK OF PROJECTION FOR 


Questions and Answers 

W E have adopted a plan of “questions and answers” cover¬ 
ing the entire work. There are a total of 842 questions, 
grouped under headings, which we hope will be of much 
assistance to the student. The number following the question 
refers to the page or pages of text in which the answer can be 
found. 

There is considerable duplication of questions. We found this 
to be inevitable, if we used the plan of grouping under headings, 
because quite often the same question would probably occur 
under three, four, or even more headings. 

We for years have refused to accede to a wide-spread demand 
for the publication of “questions and answers,” and such re¬ 
fusal has cost us many thousands of dollars. But the I. A. T. S. E. 
and M. P. M. O. International office has indorsed a book on mo¬ 
tion picture projection which contains many pages of what 
amounts to examination questions, with the answers directly ap¬ 
pended thereto, and inasmuch as the organization has officially 
approved of the proposition we see no reason for further refusing 
to publish questions and answers, but have tried to do it in the 
way which will be least objectionable. 

Action of Light 

Question 

1—Quote law relating to light intensity at different distances 


from open light source and explain its operation. ... 125-161 

2— What is meant by “absorption of light”?. 19 

3— What is meant by an “Actinic Ray”?. 19 

4— What is meant by “Angle of Incidence”?. 222 

5— What is meant by “Angle of Reflection”?. 222 

6— What is meant by “Angle of Projection”?. 20 

7— What is a “Standard Candle”?. 23 

8— What is a “candle foot” or “foot candle”?. 23 

9— What is a “Candle Meter”?. 23 

10— What is the “critical angle”?. 26 

11— What is chromatic aberration?. 130 

12— Diverging beam. What is it?. 26 

13— What is meant bv diffusion of light?.27-222 

14— Does law referred to in question 1 apply to beam be¬ 
tween projection lens and screen?. 125 

15— What is meant by “refraction”?. 126 

16— What elements control amount of bending rays receive 

in passing from air to glass?.127-128 

















MANAGERS AND PROJECTIONISTS 


911 


17—For practical purposes what may we assume the amount 
of refraction rays will receive in passing through a lens 
will depend? . 129 


Lenses 

18— Explain the difference between a piano convex, a me¬ 
niscus and a bi-convex lens.168-169 

19— What is the principal axis of a lens?. 126 

20— What is meant by working distance?.129-152 

21— What is meant by conjugate foci?. 126 

22— What do you understand equivalent focus to mean?.. 129-152 

23— What is spherical aberration?. 129 

24— What is chromatic aberration?.130 

25— What does focal length mean as applied to a simple 

lens? . 134 

26— Explain, roughly, the action of light through a lens.... 131 

27— What is meant by correcting a lens?. 134 

28'—Explain how an image is formed.133-134 

29— How is curvature of simple lenses determined?.134-135 

30— Is it possible to focus an object having area to a 

point? .133-135-136 

31— Why is it impossible to focus the condenser beam to a 

point? .. 133-135-136 

32— What relation has revolving shutter to lens diameter?.. 208 


Lenses—Projection Lens 


33— What is a projection lens?. 38 

34— What is the function of a projection lens? What does 

it do? . 126 

35— Of what elements does a projection lens consist?. 136 

36— What is meant by the “front factor” and “back factor” 

of a projection lens?. 136 

37— Which lenses of a projection lenses are cemented to¬ 
gether. and with what are they cemented?. 136 

38— What is the optical effect of cementing the lenses of the 

front factor together?. 144 

39— Are the lenses of the back factor always separated by 

spacing rings? . 136 

40— What occasionally happens, or what may happen to the 

cement (balsam) between the front factor lenses?. 137 

41— Should or should not the lenses of projection lens be 

clamped tightly in their individual mounts?. 138 

A 2 —How should GundGrb-Manhattan lenses be re-assemblod? 139 

43— Is it possible to repair a projection lens if one of its 

lenses be broken?. 139 

44— Should broken lens referred to in question 43 be sent to 

manufacturer? . 139 

45— Have odd lenses, or combinations of lenses, any value?.. 139 


























912 HANDBOOK OF PROJECTION FOR 


46— What limits the maximum diameter of a projection lens 

of given E. F. ?... 139 

47— What data is it necessary to send when ordering a new 

projection lens? .. • ... 139 

48— What range of focal lengths of projection lenses are 

carried in stock?. 140 

49— What is it necessary to do when you wish to order a 

projection lens to match one you already have?. 140 

50— Can markings of projection lenses be depended upon for 

accuracy ? .. • • 140 

51— What effect, other than light loss, has an accumulation 

of dirt on surface of lenses?. 146 

52— Name two faults for which projection lenses must be 

corrected? How is it done?. 132 

53— How is lens diameter affected by revolving shutter?.... 208 


54—Do you thoroughly understand the lenses you are 
using ? 


Practical Projection Optics 

Under this heading will be found many things duplicated in 
other sections. This is necessary, because, as a matter of fact, 


practical projection optics really includes about everything. 

55— What is brilliancy of arc crater per unit area?. 392 

56— Upon what does total light giving power of crater 

depend ? . 392 

57— What effect has distance of light source from collector 

lens on light delivered to the spot?. 162 

58— What is “working distance” of projection lens?. 152 

59— What is “Equivalent Focus”?. 152 

60— Describe universal system of lens measurement. 153 

61— Why should lenses be kept perfectly .clean ?.137-141 

62— Name some satisfactory solution for cleaning lens. 137 

63— Name cheap liquid which will remove oil from lenses 

and clean them very well. 139 

64— What kind of cloth or skin should be used to polish 

lenses? . 137 

65— How often should interior surfaces of projection lenses 

be cleaned? . 138 

66— How often should you examine and clean exterior sur¬ 
faces of projection lenses?. 137 

67— What will be the result of wrongly re-assembling 

elements of projector lens?. 138 

68— What is guiding rule for re-assembling?. 138 

69— What happens if interior of projection lens barrel is not 

kept black? . 138 

70— Why is diameter of projection lens of great importance? 

147-148 and 186 to 190 

71— Is it desirable to have projection lens diameter greater 

than is necessary to receive the entire beam?. 148 

























MANAGERS AND PROJECTIONISTS 913 

72— How can you test projection lens for distortion?. 148 

73— What is it you really do when you “focus” the picture?.. 149 

74— Can you alter the E F of a projection lens by changing 

length of barrel?. 150 

75— Can the same projection lens be used to project differ¬ 
ent size pictures?.150-154 

76— How would you calculate the size of picture a lens will 

project at given distance if you knew the size it will 
project at another distance?. 154 

77— How would you measure the focal length of a lens?. .150-153 

78— How would you measure the E F of a lens?. 152 

79— What effect has the E F of a lens on picture size at given 

distances? . 154 

80— Are lenses made in the United States satisfactory?. 156 

81— Under what conditions are anastigmat lenses of value?.. 156 

82— Are so-called “lens tables” of any value?. 158 

83— Describe projector optical train in detail. 160 

84— Can projector optical system be judged by ordinary 

standards ? . 160 

85— Name difficulties projection lens labor under. 160 

8'6—Explain practical operation of law of light quoted page 

161, and tell us how you would prove its correctness.... 161 

87— What is the first problem to be considered with relation 

to projector optical train?. 163 

88— Of how many lenses may condenser be composed?. 164 

89— What is effect of discolored condenser lenses?. 164 

90— What is effect of “pitting” of collector lens?. 165 

91— What is correct thickness of condenser lens edge?. 165 

92— Name objections to too-thin and too-thick condenser 

lens edge . 165 

93— What importance is attached to accurate curvature and 

polish of condenser lenses?. 167 

94— Explain, in detail, exactly what condenser does... 172 

95— Name types of condenser used and give full diameter 

of lenses and diameter free opening. 168 

96 — What difference is there whether convex or piano sides 

of plano-convex lenses be together?... 168 

97— Under what conditions would you use meniscus bi-convex 

combination ? . 169 

9g—What advantage has meniscus bi-convex over plano-con¬ 
vex under some conditions?. 169 

99—Under what conditions would you reduce diameter of 


100 — Name one serious objection to large diameter condenser. 170 

101— How close should condenser lenses be to each other?- 170 

102— Whv should condenser lenses not be in actual contact?.. 170 


103 — Why should condenser lenses be not more than l/16th 

apart? ..... J70 

104— Explain why spacing condenser lenses wastes light. 171 

105— To what is condenser breakage usually due?.171-172 






























914 


HANDBOOK OF PROJECTION FOR 


106— Is floor of arc crater of even brilliancy?. 172 

107— Why should crater not be focused sharply at film plane? 172 

108— What beneficial effect has spherical aberration?. 172 

109— What importance attaches to shape of spot?. 174 

110— Give your views as to proper size of spot. Tell us ad¬ 
vantages and disadvantages of large and small spot. 174 

111— In what ratio will light source be magnified at spot?... 175 

112— What percentage of total condenser area does slide car¬ 
rier cover? . 177 

113— Is light source image inverted at spot?. 177 

114— Explain ghost zone in condenser beam.177-178-179 

115— What causes blue spot in center of screen when condenser 

is advanced too far?. 179 

116— To what may we attribute fact that same film print often 

shows great “depth” in the screen image in one theatre 
than in another?. 180 

117— Is evenness of illumination essential to depth in pictures? 180 

118— Explain why evenness of screen illumination is impossible 
unless entire light beam enters projection lens... 181-182-183 

119— Explain why light beam diverges between aperture and 

lens, and what controls amount of divergence. 184 

120— Explain effect of distance of condenser from aperture on 

divergence of beam between aperture and lens. 184 

121— Explain possibilities for light loss by reason of divergence 

of beam between aperture and projection lens.... 186 to 194 

122— Explain universal method of ascertaining condenser fo¬ 

cal length and aperture distance with relation to projec¬ 
tion lens diameter.194 to 198' 

Revolving Shutter 

123— Is revolving shutter an integral part of projector opti¬ 
cal system? . 206 

124— What effect has it on lens diameters?. 206 

125— What is correct position of shutter as to its distance 

from lens? . 206 

126— How may this position be found?.206-207 

127— What is the reason, and the only reason, for or advantage 

in locating revolving shutter at aerial image?. 207 

128— Does increase of lens diameter demand increase in master 

blade of revolving shutter?. 208 

Practical Projection 

129— What various things does the term projection include?.. 213 

130— What does the term projectionist mean?. 39 

131— What must the competent modern projectionist know?.. 214 

132— In what way does the projectionist redirect the photo¬ 
play? .... 214 

133— In what way is projection hampered, insofar as concerns 

artistic results, by wrongly made “schedules”?. 215 

134— What is correct way to make a schedule?.216 
























MANAGERS AND PROJECTIONISTS 915 

135— Who practices over-speeding?. 216 

136— What is the practical effect of over-speeding?.216-217 

137— Does correct projection speed very often vary with indi¬ 
vidual scenes in a production?.217 

138— What is correct projection speed, and why is it that ad¬ 
joining scenes often very?. 217 

139— What is one of the very highest functions of the pro¬ 
jectionist? .217 

140— Over-speeding projection, and what it really is. 218 

141— Rear projection—when is it practicable?. 233 

142— Is rear projection with screen at proscenium line and 

projector on rear of stage practicable?. 233 

143— Exactly what is meant by “screen brilliancy”?. 43 

144— Tell us why a leader and tail-piece should be used. 284 

145— Why should tail-piece be opaque?. 285 

150— Should white light ever be allowed to show on screen 

at end of reel?. 286 

151— Explain relation of revolving shutter to lens diameter.. 208 

Distortion of Picture 

152— Explain what effect a side view of the screen has on 

apparent shape of objects thereon. 252 

153— Draw diagram showing exactly how much any given side 

view will reduce width of object viewed. 252 

154— Why is it objects on screen look abnormally tall when 

viewed from heavy side angle?. 253 

155— What is meant by keystone effect?. 253 

156— Explain why bottom of picture is wider than top when 

projection is downward.253-254 

157— How would you calculate the exact amount of distortion 

(keystone) any given angle and distance of projection 
would produce? . 254 

158— Why is projection angle not a safe guide as to amount 

of distortion produced?. 255 

159— What is best guide in matter of limit of projection 

angle? .255-256 

160— What effect has added projection distance on distortion, 
lens height above screen center remaining the same ?. .. . 256 

161— In what proportion does added angle of projection dis¬ 
tort the picture?. 257 

162— Does making sides of picture perpendicular remove pic¬ 
ture distortion? . 257 

163— Wherein lies the evil of picture distortion?. 257 

164— Can a picture be projected at an angle without distor¬ 
tion? . 254-255-256-257 

165— How can you make sides of the picture parallel when 

there is pitch in projection?. 258 

166— Is keystone effect accompanied by out of focus?. 258 

167— How may out of focus effect due to pitch in projection 

be overcome? . 258 





























916 HANDBOOK OF PROJECTION FOR 

Size of Picture 

168— Is there any real necessity for a picture wider than eigh¬ 
teen feet? . 243 

169— Does large picture make front seats less valuable ?.244 

170— What should be minimum distance from front row to 

screen with a 16-foot picture?.. 244 

171— Explain why being too close to a large picture sets up 

heavy eye strain. 244 

172— What effect has size of picture upon definition?. 245 

173— What effect has picture size upon light necessary to 

secure a given degree of brilliancy?.. . 245 

174— What effect has picture size upon making defects in 

photography, “rain,” etc., visible?.. ; .246 

175— What effect has picture size in making side motion of 

film in projector aperture visible?. 246 


The Screen 

176— What do you understand by “picture light”?. 219 

177— What is the sole function of screen surface?. 219 

177a—Is it practicable to compare screen surfaces and form 

an intelligent opinion as to their relative merits by look¬ 
ing at screejis in different theatres? If not, why not?.219-220 

178— Is it even possible to form sure judgment as to relative 

value of screen surfaces by substituting one surface for 
another while a picture is being projected?. 220 

179— How may a reliable comparative test be made?. 220 

180— What screen salesman should be obliged to do before 

you buy . 221 

181— What three kinds of reflection are there? Describe 

them .222-223 

182— What is diffuse reflection?. 222 

183— Has visible roughness of screen surface any advantage? 223 

184— What is interfering light?. 224 

185— Name causes of interfering light. 224 

186— How would you test screen for interfering light?. 224 

187— Interfering light injures screen results, hence box office 

receipts . 225 

188— Duty of projectionists to study screen surfaces. 221 

189— What is fundamental requirement of screen surface?.. 225 

190— What kind of material should be used for cloth screen? 226 

191— How would you clean a plaster screen?. 226 

192— What increases reflecting power of paint?. 227 

193— How would you mix a screen paint?. 227 

194— Can a painted screen be washed?. 229 

195— Is a kalsomine surface a good screen?. 229 

196— How often should kalsomine screen surface be renewed? 229 
196a-Before painting or kalsomining a cloth screen how 

would you proceed to “size” it?. 230 




























MANAGERS AND PROJECTIONISTS 


917 


197— How would you test your painted or kalsomined screen 

as to its condition?. 230 

198— Neat cement surface—what about it?. 230 

199— What advantage has the metalic surface screen?.230 

200— Over what viewing angle does brilliancy of metalic sur¬ 
face screens extend?. 230 

201— What faults have metalic surface screen surfaces besides 

narrowness of viewing angle?. 230 

202— Is it advisable to attempt making home-made metalic 

surface screens? . 231 

203— Mirror screens—of what do they consist?. 231 

204— Name peculiarities of mirror screens and one of prin¬ 
cipal objections to them.231-232 

205— Of what may a translucent screen be made?. 232 

206— How is film placed in projector when using translucent 

screen ? . 232 

207— What objection is there to cloth translucent screen?_232 

208— What is the best translucent screen?.233 

209— Under what condition may there be advantage in concave 

screen surface? . 233 

210— What height above floor should screen be located?. 234 

211— What should be location of screen with relation to lens? 239 

212— With what should the picture be outlined?. 240 

213— Should picture over-lap border, and why?. 240 

214— What is effect of picture border?. 240 

215— What color is best for border?. 241 

216— Of what character should finish of screen surroundings 

be? . 243 

217— Why should you paint stage floor black?. 243 

218— Are tinted screen surfaces desirable?. 246 

219— Is it desirable to locate screen at front of house?. 247 

220— If screen is to be located on stage what advice would 

you give in the matter?.247-248 

221— Describe right way to mount screen.249-250-251-252 

222— What two important points must be considered in screen 

surfaces? . 261 

223— Into what three classes may screen surfaces be grouped? 260 

224— How would you apply the knowledge contained in tables 

12 to 17 in practice?. 263-264 

225— Within what viewing angle is efficiency of ordinary com¬ 
mercial screens confined?. # . 263 

226— Name the good diffusing surfaces in table 14.......... 263 


Glare Spots 


227— What is a “glare spot”?. 237 

228— What should be limit of brilliancy of any spot of light 

visible to audience?. 237 

229— Is there any excuse for glare spots?. 238 

230— Name the various glare spots most common. 238 

































918 HANDBOOK OF PROJECTION FOR 


231—How may clock be made plainly visible without being a 


glare spot? .238-239 

232— How may exit signs be made conspicuous without being 

glare spots? . 239 

233— Is fact that no one complains of glare spots proof that 

they are doing no damage?. 239 

Flicker 

233a-To what is flicker due?. 613 

234— Is there any excuse for flicker due to opening and clos¬ 
ing of projection lens by revolving shutter?. 235 

235— Explain action of flicker upon the eye.235-236 

236— Is flicker due to wrong procedure in projection?. 235 

237— Does brilliancy of screen surface effect flicker?. 235 


The Film 


238— Exactly of what does a film consist?. 268 

239— Describe the process of its manufacture. 268 

240— What is standard thickness of film?. 269 

241— What are standard perforation and film dimensions?_269 

242— Name a few of the more prolific causes of damage to 

film . 270 

243— What is “rain”?. 271 

244— Name one chief cause of “rain”. 271 

245— Name chief causes of damage to sprocket holes. .. .271-272 

246— Should film repairing be done by anyone other than a 

thoroughly competent person?. 272 

247— To what is damage to film in passing through projector 

mostly due? . 272 

248— What troubles may badly matched sprocket holes cause? 

273-275 

249— In what way may projectionist increase the tendency 

of emulsion to deposit on tension shoes?. 273 

250— Do poorly made splices do harm?. 275 

251— Should splices be made with the unaided fingers?. 277 

252— What is correct width of film splice?. 277 

253— What is of immense importance in the making of a splice? 278 

254— What is the greatest fault found in film splicing?.... 279 

255— How may film be measured as to its length?. 292 


Film Inspection and Repair 

256— What repairs should projectionist make on film?. 286 

257— Does price exhibitor pays for film service include in¬ 
spection and thorough repair of film?.286 287 

258— Should projectionist be paid extra for time employed in 
inspecting and repairing films received from exchange 

in bad condition?.287-288 

259— Describe the usual exchange “inspection”. 288 




























MANAGERS AND PROJECTIONISTS 919 

260— What should projectionist do when using films on cir¬ 
cuit? . 288 

261— How may dry film be moistened?.289-290 

262— With what may film be cleaned?.290-291 

263— Film splices. 277 

The Rewinder 

264— Where should the rewinder be located?. 332 

265— What importance attaches to perfect lining of the two 

rewinder elements? . 332 

266— How would you arrange rewinder table for the making 

of splices? . 332 

267— How fast should rewinder run?. 333 

268— Should there be a brake on rewinder, and where should 

it apply its power and why?. 333 

269— Should rewinder motor be arranged to stop automatically 

when end of film is reached?. 333 

270— What damage does “pulling down” do?. 333 

271— Name one big advantage of slow rewinding. 333 

272— Should there be a separate hand rewinder?. 334 

Batteries 

273— Describe a “wet” battery. 6-7 

274— What is voltage of one cell battery?. 7 

275— Which pole of a battery is positive?. 7 

276— Can any voltage and amperage be generated by batteries ? 7 

277— For what are batteries mostly used?. 7 

278— Can dry or wet batteries be connected in multiple or 

series ? . 897 

Electrical Terms and Measurements 

279— What is an ampere? What does it represent?. 51 

280— What is an “ampere hour”?. 20 

281— What is an ammeter?. 19 

282— What is an “ampere turn”?. 20 

283— What is an electric arc?. 20 

284— What is arc voltage drop?. 20 

285— What is meant by carrying capacity?. 23 

Electrical Action 

286— Is it essential that the projectionist understand electrical 

action ? . 3 

287— What is necessary to the understanding of electrical 

action ? . 3 

28'8—What is electricity?. 3 

289— Polarity. What is it? Explain fully....3-50 

290— Of what does every electric circuit consist?. 3 

291— What is an ampere?. 51 

































920 


HANDBOOK OF PROJECTION FOR 


292— What is a volt?. 50 

293— What is voltage and to what does it correspond?.50-51 

294 — Explain why positive seeks negative.... 4 

295— Explain how power is stored up, using steam, a spring 

and electricity as examples.. 5 

296— Can you see or feel electricity? Explain your answer.. 5 

297— Has positive or negative wire of a generator any affinity 

for anything else except opposite polarity of same gen¬ 
erator ? ... 6 

298— Assuming a generator of high voltage to be thoroughly 
insulated, together with all its connections, could you 
stand on wet earth and handle either wire with safety? 6 

299— Does current seek to escape from wires to earth?. 5-6 

300— Assuming a ground on both positive and negative, will 

there necessarily be current leakage ?... 6 

301— What would happen if uninsulated positive of one gen¬ 
erator touched uninsulated negative of another generator? 6 

302— Describe action of A. C. and explain diagram Fig. 4_15-17 

303— What is difference between D. C. and A. C. ?. 13 

30-1—What is meant by current “frequency”?. 29 

305— For what service is low frequency desirable; for what 

service is it undesirable?. 16 

306— Why should projectionist understand effect of current 

frequency ? .... 16 

307— Low frequency current produces a flickering light. Why? 15 

308— Explain effect of 2-phase and 3-phase current as com¬ 
pared with single phase. 18 

309— In diagram, Fig. 4, what does slope in sides of triangles 

represent? .16-17 

310— Does current “flow” from positive to negative?. 13 

311— Explain relation of volts and amperes to horse power.. 14 

312— Insofar as power be concerned, is there any difference 

between 100 amperes at 5 volts and 5 amperes at 100 
volts? •..53-54 

313— What are standard frequencies for commercial work?.. 15 

314— What is advantage of two or three phase over single 

phase? . IS 

315— What is meant by “voltage drop”?. 20 

316— What is a “ground”?. 30 

817—What is meant by “magnetic density”?.. 33 

318— What is meant by “multi phase”?. 34 

319— Parallel or multiple connection. What is it?. 37 

320— Ratio of transformation. What is it?. 40 

321— Residual magnetism. What is it?. 41 

322— Magnetic saturation. What is it?. 42 

323— How work is accomplished by electricity. 52 

Measurements and Calculations 

324 — In electrical calculations what do the letters E, C and R 

stand for ?..... 54 




























MANAGERS AND PROJECTIONISTS 921 

325— What is-a “mil”? A “circular mil”?..24-34-70 

326— Into how many degrees is every circle divided?. 24 

327— Upon what does the width, measurement in inches, across 

a degree depend?. 24 

328— If a circle be 36 inches in circumference, how wide 

would one degree of it be in inches?. 24 

329— Describe a B. & S. wire gauge. 78 

330— What other tool may be used to measure round wires ?.. 78-79 

331— In a common fraction what does the horizontal line 

indicate ? . 54 

332— Horsepower, what is it?. 30 

333— Horsepower, electrical, what is it?. 30 

334— In calculating resistance of projector arc circuit in what 
way do we make allowance for resistance of arc itself? 58 

335— Explain how you would calculate resistance in ohms if 

amperes and voltage were known?. 55 

336— What is “Ohm’s Law”?. 55 

337— How would you calculate number of amperes a known 

voltage will force through a known resistance?. 55 

338— For purposes of calculation what is meant by “arc 

voltage constant”? . 56 

339— How would you calculate ohmic resistance of projector 

arc? . 57 

340— How would you calculate area of cross section of round 

wires ? . 77 ^ 

341— How would you calculate capacity of any round copper 

wire ? . 77 

342— How would you calculate voltage drop of circuit carry¬ 
ing a known amperage?. 75 

343— How would you calculate size of wires to carry given 

amperage at given voltage drop?. 76 

344— How would you determine whether or not any circuit is 

operating economically ?.. 76 

345— What is the area of cross section of a wire )/% inch in 
diameter? Of a wire 100 mills in diameter? Of a wire 

inch in diameter?. 77 

346— How would you calculate voltage it would take to force 

given number of amperes through a known resistance?.. 55 

347— What is the area of cross section of a wire 1/1000 inch 

in diameter?. 77 

348— What does “squaring the diameter” mean?. 77 

349— How many horsepower in 10,000 watts?. 77 

350— Kilowatt hour, what is it?. 31 

351— As applied to motors, generators, etc., what is meant by 

the term “efficiency,” and how is it measured?. 27 

Electric Generators, or Dynamos 

352— Upon what law is action of generator (dynamo) based? 7 

353— Explain action of elementary generator, Fig. 1. 7 

354— What is an armature?... 21 





























922 HANDBOOK OF PROJECTION FOR 

355— All armatures generate alternating current. Explain why 7 

356— What is an armature coil?. 21 

357— Explain commutation—how direct current is obtained.. .9-10 

358— Are all armature coils inter-connected?. 11 

359— Describe electric generator as shown, Fig. 1. 11 

360— Upon what will voltage and amperage of generator 

illustrated in Fig. 1 depend?. 11 

361— How is current generation started in a dynamo?. 12 

362— What is meant by a balanced armature?. 21 

363— What is a “brush” and what is meant by “brush loss”?.. 22 

364— How many polarities has a generator?. 4 

365— What is meant by a “field coil”?. 11 

366— What is it generates magnetic lines of force?. 11 

367— What is meant by a “permanent magnet”?. 12 

368— What is meant by “residual magnetism”?. 12 

369— What is the practical effect of passing current through 

a field coil?. 12 

370— What is meant by “magnetic saturation”?. 12 

371— May a generator have more than two poles?. 13 

372— What is effect of additional poles—more than two?_ 13 

373— What is meant by front and back end of armature?.... 21 

374— Describe generator armature. 21 

375— What is a constant current dynamo?. 25 

376— What is a “field rheostat” and what is it for?. 28 

Insulation 

377— What is the purpose of insulation?. 80 

378— What class of substances do we call “insulating ma¬ 
terials” ? . 80 

379— Name several insulating materials. 80 

380— Of what does rubber covered (R. C.) insulation con¬ 
sist? .80-81 

381— Under what conditions and why is coating copper wires 

with tin necessary?. 81 

382— With increase of what element is it necessary to increase 

insulation resistance? . 81 

383— Is it necessary to vary character of insulation under 

different conditions of service?. 81 

384— Name three types of insulation.80-81-82 

385— Where is use of weatherproof insulation permissible?.. 81 

386— May R. C. be used wherever weatherproof may be 


387— May R. C. be used where slow burning is required?. .82-83 

388— What determines number of layers of braid necessary 

in R. C. wire?. 83 

389— Why are R. C. wires rated at lower capacity than wires 

having other types of insulation?. 83 

390— Where is it permissible to use varnished cloth insulation? 82 

391— What is principal difference in R. C. and other insula¬ 
tions? . g2 

































MANAGERS AND PROJECTIONISTS 


923 


392— What type of insulation is necessary in conduit?. 83 

393— What single braid R. C. wires may be used in conduit? 83 

Fuses 

394— What is the purpose of fuses?. 107 

395— Explain Figure 19, page 107, in detail. 107 

396— Exactly what is it happens when a fuse “blows”?. .107-108 

397— Will fuses carry more than their rated capacity?. 108 

398— Explain how and why fuses protect wires and apparatus 108 

399— In what way do fuses prevent operation of faulty cir¬ 
cuits? . 108 

400— What types of fuses are used in theatres?.108-109 

401— What markings should be stamped on fuses?. 118 

402— Name points at which fuses must be installed. 119 

403— What fuses should main house board carry?. 99 

404— Describe a cartridge fuse in detail.109-110 

405— Describe two types of cartridge fuses. 109 

406— May ferrule contact fuse be used for any amperage?.. 109 

407— Describe pilot wire of cartridge fuse. What is it for? 109 

408— In what way are you supposed to tell whether or no a 

cartridge fuse is blown?. 109 

409— Describe difference in cartridge fuses for different 

voltages .112-113 

410— What is a “plug” fuse? Describe it.110-111 

411— Can plug fuses be used on any amperage?. Ill 

412— May plug fuses be used for any sort of service?. Ill 

413— What is meant by “boosting” fuses?.111-114 

414— Is boosting fuses dangerous?.111-114 

415— What should be done to projectionist caught boosting 

fuses? . 114 

416— What should be done with old fuses?. 114 

417— Is it practical to re-fill old fuses?. 114 

418— Why is it unnecessary to fuse projector arc circuit 

closely? . 114 

419— How would you determine necessary size fuses for pro¬ 

jector arc circuits when using motor generator, rotary 
converter or mercury arc rectifier?.115-116 

420— Is it practical to operate temporarily, in an emergency, 

with only one fuse on 2-wire circuit?.116-117 

421— Is it possible, in emergency, to fuse with copper wire?.. 117 

422— Is it possible for a faulty fuse contact to blow a 

fuse? . 117-118 

* 423—Draw sketch of, or describe, a practicable tester for 

both plug and cartridge fuses. 118 

424— Describe fusing of emergency light circuits. 120 

425— How should exit lights be fused?. 120 

426— Describe acceptable method of double fusing projector 

arc circuits. Why should it be done?.. . 120 

427— What circuits may you fuse 25 l>er cent, above capacity 

of apparatus attached thereto?. 114 
































924 


HANDBOOK OF PROJECTION FOR 


428— Which side of projection room main switch should main 

fuses be placed on and why?. 342 

Wire Systems 

429— Of what does every electric circuit consist, insofar as 

concerns electrical action?. 3 

430— Describe and draw sketch of 2-wire system. 84 

431— Describe and draw sketch of 3-wire system.85-86 

432— Can projection arc be operated from series arc system? 84 

433— Can you connect projector arc lamp to 2-wire system 

at any point ?.84-85 

434— What do you understand by “commercial voltage” ?... . 85 

435— What book will supply traveling projectionist data on all 

power plants of country?. 85 

436— What, in effect, is the 3-wire system?.85-87 

437— Upon what basic principles does 3-wire system operate? 85 

438— Explain what the neutral wire is. 18 

439— What relation does voltage between outside wires of 
3-wire, and voltage of either outside and neutral bear 

to each other ?.85-86 

440— How many wires are usually found in 2-phase circuits? 

In 3-phase circuits?. 18 

441— What is the true positive and negative of 3-wire system? 86 

442— Is neutral both positive and negative? Explain. 86 

443— What is advantage of 3-wire system?. 87 

444— What is meant by “balanced load” on 3-wire?. 88 

445— How would you test balance of load on 3-wire?. 90 

446— How would you calculate whether or no a circuit was 

operating economically ? 76 

447— Explain effect of unbalanced load on 3-wire. 88 

448— Explain effect of neutral fuse blowing when load is bal¬ 
anced and unbalanced.88-91 

449— Is one wire of Edison 3-wire always grounded?. 353 

450— You connect a 2-wire circuit to each side of 3-wire feed¬ 

ers, and to each circuit so connected you connect one 60- 
watt lamp. What is the effect? How much current 
would flow in neutral?. 87 

451— Connect 10 Amp. motor to one side of 3-wire circuit, 

and lamps using 7 amperes to other. How much cur¬ 
rent would each fuse carry?.Figure 10, page 86 

452— If 110-volt lamps using 40 amperes be connected to one 

side of 3-wire circuit and 110-volt motors using 40 am¬ 
peres to other side, what will effect be ? How much 
will neutral fuse carry?....Fig. 11 and page 90 

453— If all wires of a 3-wire projection room cutout are fused 
at 60 amperes, and to one side apparatus using 30 am¬ 
peres is connected and to the other side apparatus using 
25 amperes, could you connect, a projection arc using 

30 amperes without changing fuses?. . .Fig. 11 and page 90 

454— How would you select wire size for 3-wire system?_ 91 
























MANAGERS AND PROJECTIONISTS 


925 


Wire Splices and Terminals 

455— Should all wires have terminal lugs?. 121 

456— How should terminal lugs be attached to wires?. 121 

457— What may happen if you cut straight in when removing 

insulation, and cut a ring around the wire?. 121 

458— Before connecting a terminal lug to binding post of 

switch or other thing, what should be done? . 122 

459— Why is it important that both terminal lug and binding 

post be perfectly clean before connecting?. 122 

460— Will all power wasted in resistance of poor joints and 

connections be registered on meter?. 122 

461— What do Underwriters’ rules require with regard to wire 

splices ? . 123 

462— Describe proper method of removing insulation prepara¬ 
tory to making splice or attaching terminal lug. 123 

463— Describe proper method of soldering wire joint. 123 

464— Describe correct method of insulating wire splice after 

it is made. 123 

465— What is a wire connector and what would you do before 

using one on stranded wire?. 124 

466— What sort of terminal lug is suitable for hot places?.. 124 

Switches 

467— Name the various types of knife switch used in theatres 92 

468— Name the various parts of knife switches. 92 

469— What care should knife switches have?.92 and 96 

470— Name one important point to be considered when in¬ 
stalling a knife switch.92-93 

471— What is meant by a single throw knife switch?. 44 

472— What is meant by a single pole knife switch?. 44 

473— What is meant by a double pole knife switch?. 27 

474— What is meant by a double throw knife switch?. 27 

475— What is meant by a triple pole, single throw switch?. . 47 

476— What does “S. P. S. T.,” “D. P. D. T.” “T. P. S. T.” 

and “T. P. D. T.” mean?. 92 

477— What is meant by an “inclosed switch”?. 94 

478— Name one absolute requirement for projector switches 94 

479— Name one rule to be observed in connecting inclosed 

switches . 94 

480— What should govern in locating switches?. 94 

481— Should emergency light switches be on main “board”? 94 

482— What should govern in locating projection room 

switches? ..... 95 

483— Is it permissible to use single pole knife switches- in 

theatres? . 95 

484— What type switch is usually used to control incandescent 

circuits in theatres?. 95 

485— Where are triple pole switches used ?. 95 

486— Where may we expect to find D. P. D. T. switches?.. 95 




























HANDBOOK OF PROJECTION FOR 


926 

487— What marks must be stamped on some part of every 

knife switch? . 96 

488— May a switch be used for higher amperage or voltage 

than it is rated for ?... 96 

489— In inspecting your switches (which should be done once 

every week) what faults would you look for?. 96 

490— When is metal switch cabinet required ?.... . 96 

491— What markings would you affix to stage switches?.... 106 


Switchboards 

492— What rules apply to switchboard installation?. 97 

493— From whom may authoritative information be had as to 

Underwriters’ rules concerning switchboards?. 97 

494 — What rules should govern in selection of location of 

main house board?.97-98 

495— Is projectionist ever placed in full charge of auditorium 

lighting, except emergency and exit?.96-97 

496— What should be done to enable projectionist to light 

auditorium in case of emergency?. 98 

497— Should switchboard be in projection room if only one 

man is on duty therein?. 98 

498— Is it important that there be close co-ordination between 

auditorium lighting and programme?. 99 

499— What circuits should main house board carry?. 99 

500— How do you trace out connections on large boards ? 

100 - 101-102 

501— Is it possible to construct an acceptable home made board 

by using porcelain base cutouts?.103-106 

502— Name a few important points in connection with stage 

switchboard . 104 

503— What type fuses must be used on stage switchboard?.. 106 

504— What fuses should stage switchboard carry?. 106 

506— How should stage switches be marked?. 106 

507— What special reasons are there why stage switches 

should be kept in first class condition?. 106 

508— Should the handling of stage switchboard be confined 

strictly to one man?. 106 

Projection Room 

509— What has location of projection room to do with dis¬ 
tortion of picture and keystone effect?.293-294 

510— If projection room floor is 20 feet above screen, will 

distortion be changed by changing distance of room from 
screen? Explain fully.253-293 

511— Will altering distance of projection change amount of 

distortion if projection angle remains same?. 255 

512— Is projection angle a safe guide as to distortion?. 255 

513— Name one serious objection to a long projection distance? 294 

























MANAGERS AND PROJECTIONISTS 927 


514— Suggest some evidence that projectionist cannot judge 

as to sharpness of focus when projection distance is 
long . 294 

515— Compare advantages and disadvantages of main floor, 
front of balcony and other projection room locations, 

nc 296 to 300 

516— What are requisites of good projection room_300 to 303 

517— What is best projection room door construction?. 303 

518— Name the requisites of good projection room floor. 304 

519— What very serious fault must be guarded against in top 

dressing of cement floors?. 305 

520— Name the acceptable forms of permanent projection 

room wall construction. 306 

521— Should electric conduit be built into the walls?. 306 

522— What ports are necessary?. 306 

523— Draw diagram illustrating size and location of the vari¬ 
ous ports . 307 

524— What should height of observation ports be when pro¬ 
jection is level, and what amount should they be low¬ 
ered for each 5 degrees added angle in projection?.... 308 

525— Describe best method of filling in lens ports.308-309 

526— Describe movable port shutter.309-310 

527— Name important reason for observation ports of ample 

size . 310 

528— Is it practical to cover lens ports with glass?. 311 

529— How should glass be set in observation ports and 

why? .310-211 

530— Do small observation ports serve any good purpose?.... 312 

531— Give your views as to port fire shutters, including best 

kind, suspension and fusing.312 to 316 

532— Why is it absolutely imperative that port fire shutter 

fuses be located very close to every probable source of 
fire? . 314 

533— In what respect do many officials err with regard to 

location of port shutter fuses?. 316 

534— Why should padding be placed under port shutters?... 316 

535— What three important purposes does projection room 

ventilation serve? . 317 


536— Why should vent flue area be the same for every size 

projection room? . 317 

537— In what respect is an open vent flue (flue without a fan) 

objectionable? . 317 

538— Of what must vent flues be made and how insulated?. . 318 

539— What fresh air inlets should there be and where located? 319 

540— What danger is there in open observation ports?. 318 

541— Explain your views as to projection room supplies and 
whether or no it pays to be to saving with them. .327-328-329 

542— What record of supplies should be kept?.328-329 

543— What proof can you offer that a too-great economy in 

projection room supplies does not pay?. 329 


























928 HANDBOOK OF PROJECTION FOR 

Projection Room Lighting 

544— What direct connection is there between brightly lighted 

projection room and small observation port?..... 344 

545— What will inevitably happen if room be unintelligently 

lighted and the observation ports small?. 344 

546— Describe observation port which permits of a brightly 

lighted room . 311 

547— Describe acceptable method of lighting room with small 

observation ports . 344 

548— Describe two-circuit method used in England. 345 

Projection Room Wiring 

549— How large must projection room service wires be?_ 338' 

550— How would you compute size necessary?. 338 

551— Using Table No. 1, page 70 and voltage drop formulas, 
pages 74 to 76, what size projection room feeders should 
you have for two 60 ampere projection arcs, two 20 
ampere dissolver lamps and a 40 ampere spot; voltage 


552— In wiring for motor generators, economizers, etc., what 

should calculations be based upon?. 339 

553— Would you consider link fuses in metal cabinet as being 

acceptable for projector circuit?. 341 

554— Is it possible to “balance the load” by connecting to op¬ 

posite sides of a 3-wire circuit, insofar as concerns the 
projector arcs? . 341 

555— What objection is there to connecting both projector 

lamps to one “side,” even though but one projector be 
running at a time?. 341 

556— What is the effect in connecting projector circuits to the 
outside wires of 3-wire system when taking current 
through resistance? This is very important.... 88-342- 

343-344 

557— Whom should you consult before connecting to 3-wire? 341 

558— What voltage motor is best when using 3-wire?. 341 

559— When using mercury arc rectifier on 3-wire would you 

connect to one side or to outside wires?. 342 

560— Is it best to purchase economizers, inductors, etc., for 
use on one side or on outside wires of 3-wire circuit?.. 342 

561— Describe method of establishing permanent ground wire 346 

562— Name the two ways projector circuits may be run. 348 

563— Name reasons why switches and fuses should be pro¬ 
tected by metal cabinet. 348 

564— Draw diagram showing connection through switch in 

such way that economizer will feed one projector lamp 
and rheostat the other, explaining when and why such a 
connection is advisable. 349 

565— Explain, by diagram, how D. P. D. T. switch may be 

used to instantly change polarity of wires. 350 




















MANAGERS AND PROJECTIONISTS 


929 


566— Show, by diagram, how two D. P. D. T. switches may 

be used to change fuses and (or) reverse polarity. 350 

567— Illustrate, by diagram, how you would arrange to change 
from one supply to another if you were using resistance 
and wanted higher amperage from one than the other, 

350-351 

568— Show, by diagram, how you would arrange to instantly 

change from rheostat to transformer. 351 

Projection Room Equipment 

569— Why should projection room equipment be ample and 


complete? . 319 

570— Should there be closets in projection room?. 320 

571— Should there be running water and toilet?. 321 

572— Name reasons why chair at projectors is desirable.321 

573— Name reasons why projection room reels are necessary 322 

574— Is it good policy to be niggardly with projection room 

supplies ? . 327 

575— Should there be an ammeter and voltmeter?. 334 

576— What tools should the projectionist have?.335-336 

577— For what is a hand bellows essential ?. 335 


Resistance 

578— What is the effect of resistance?. 53 

579— When current is made to flow against resistance, hence 

to overcome it, what is consumed?. 56 

580— Explain your understanding of what wire capacity is 

based on . 64 

581— What is the immediate effect of overloading a wire?.... 64 

582— Name the two reasons why wires should never be worked 

above capacity . 64 

583— Resistance of a circuit increases or decreases with 

what? . 64-65 

584— Taking resistance of copper as 1, what is relative re¬ 
sistance of some other metals?.65-68 

585— What effect has rise in temperature on resistance of 

wires or metals? On resistance of carbon?. 65 

586— Is resistance in metals directly proportional to increase- 

of temperature over normal?. 66 

-587—What is “normal temperature”?. 66 

588— At what temperature is resistance of wires, as given in 

tables, calculated ? 66 

589— Describe the properties of some metals used for re¬ 
sistance . 67 

590— To what point is the resistance of a wire constant, re¬ 
gardless of amperes flowing?.68-71 

591— What is the economical limit of current flow in any 

circuit ? . 69 


























930 HANDBOOK OF PROJECTION FOR 

592— What marks the limit of capacity of copper wires, solid 

and stranded ? .... • • ™-7 J 

593 — What is meant by “mil foot standard of resistance ?.. 73 

594 — What is the mil foot resistance of copper at 75 deg. F.. 73 

595 — How would you apply mil foot standard in measuring 

resistance of circuits?. 73 

596— How would you calculate resistance of a copper wire of 

known size and length?.••• • 73 

597_How would you figure the voltage drop of a circuit?.74-75-76 


598— How would you figure wire size for given amperage to 

give any desired voltage drop?.•. 76 

599 — Why is resistance, or its equivalent, necessary in pro¬ 
jection arc lamp circuit?. 413 

600— Is there difference between resistance offered by the 

circuit when carbons are froze and when arc is burn¬ 
ing? .391 and 376 

601— What do you understand by “fixed” and “variable” re¬ 
sistance as applied to rheostats?. 415 

602— Explain, in detail, exactly what takes place when you 


603— What is objection to overloading (over-heating) the 

coils or grids of a rheostat?. 417 

604— In what practical way can you tell whether or no your 

rheostat coils are over-loaded?. 418 

605— What two important points are there to remember in 

considering insulation of rheostat coils or grids?. 418 

606— Why should rheostat, as a whole, be insulated from 

earth? . 419 

607— Why are iron wire rheostats undesirable?. 422 

608— What is chief objection to large grid rheostats?. 422 

609— How would you make temporary repair if coil burned 

out? . 423 

610— Draw diagram of two rheostats connected in series. 424 

611— What is effect of connecting rheostats in series?. 424 

612— How would you figure amperage flow from two or more 

rheostats connected in series?. 424 

613— Draw a diagram of multiple (parallel) rheostat con¬ 

nection, and tell us what the practical results of such a 
connection are .424 to 427 

614— Could you use two 110-volt rheostats in series on 220 

volts ? . 426 

615— Could you use two 110-volt rheostats in multiple on 220 

volts. Explain reasons for your answer.426 

615a-Could you use a 110-volt rheostat on 150 volts?.427 

616— Is there any such thing as an A. C. or D. C. rheostat?.. 427 

617— Voltage being equal, will a rheostat deliver same am¬ 
perage on A. C. and D.C. ? Explain your answer.427 

618— What amount of waste is represented in a rheostat?.... 428 


























MANAGERS AND PROJECTIONISTS 


931 


619— What amperage would result from the connection of one 

110-volt, 25-ampere, and one 110-volt, 40-ampere rheo¬ 
stat connected in multiple? In series?. 429 

620— Show, by sketch, how coils are attached to and insulated 

from frame of rheostat.433 

621— What amperage would you get from one 50-volt, 15- 

ampere, one 110-volt, 40-ampere and one 220-volt, 25- 
ampere rheostat on 220 volts?. 429 

622— Explain how you would disassemble a wire coil rheo¬ 
stat . 435 

623— Explain electrical action of the new multiple unit coil 

rheostats ..437 to 441 

Grounds and Testing for Same 

624— Does a “ground” necessarily mean that connection is 

had with earth?. 352 

625— What is real meaning of term “ground”?. 353 

626— Is neutral of Edison 3-wire system grounded?. .353 and 354 

627— If both positive and negative have connection with earth, 

will there necessarily be current leakage?. 354 

628— What is reason for grounding Edison 3-wire neutral?.. 354 

629— Is neutral of Edison 3-wire grounded at more than one 

pojnt? . 354 

630— Will test lamp show light from neutral to ground?.... 355 

631— What possible effect might result from placing rheo¬ 
stat in neutral of Edison 3-wire circuit?. 355 

632— Is it possible, theoretically, to ground lower carbon, 

disconnect neutral and strike an arc? Explain. 355 

633— Name various things available for testing for ground.. 356 

634— Describe, using diagram, test lamp for 110-220 volts. . 356 

635— Should projector ground wire be disconnected when 

testing for grounds?. 357 

636— Is a battery test reliable for grounds in projector cir¬ 
cuit? . 357 

637— What is the best test of all for grounds?. 357 

638— Describe how you would locate grounded Goil in your 

rheostat . 360 

639— How would you test the rheostat as a whole?.358-359 

640— Why should the projector always be grounded?. 360 

641— What is effect of ground in projector lamp?.360 

642— How often should lamp be tested for grounds?. 361 

643— Describe method Auerbach used for testing.346 and 347 

644— How would you install permanent ground wire for 

testing ? .346 


The Projector 

645— What are dimensions of standard aperture?..... .20 and 608 

646— Is it good business policy to keep projectors in use for 

too long a time?. 329 


























932 


HANDBOOK OF PROJECTION FOR 


647— Describe method of anchoring projector to floor.334 

648— What damage is done by using intermittent sprocket 

for too long a time?... 328 

649— Why is excess of oil on projector mechanism bad?.... 593 

650— Why is a too-thin oil objectionable?. 593 

651— Is more than one grade of lubricant necessary ?..... 593 

652— Name objections to a too-thin and a too-heavy oil-593 

653— What important rule must be observed in lubricating a 


654— Name reasons why intermittent oil well should have spe¬ 
cial high grade lubricant. 594 

655— Would you use graphite in intermittent oil well?.595 

656— Should gears be washed off at stated intervals?.595 

657— Should intermittent oil well be washed out?. 595 

658— Give your ideas as to take-up tension. 595 

659— What harm will dirt on face of sprockets do?. 596 

660— Should intermittent movement be so closely adjusted that 

sprocket has no circumferential movement?. 598 

661— Is it good practice to have a spare intermittent move¬ 
ment on hand?. 599 

662— Would you try to make a new star run with an old cam, 

or vice versa?. 599 

663— Describe correct way to remove an old intermittent 

sprocket from shaft and install a new one.600 

664— Are taper pins used to pin intermittent to shaft, and 

how would you tell small end?. 601 

665— What do you understand by “undercut” as applies to 

sprocket teeth? . 602 

666 — What harm do worn intermittent sprocket teeth do?.... 602 

667— Why do intermittent sprocket teeth wear fast?. 602 

668 — What is the gate tension for?. 603 

669— How would you adjust the gate tension?. 604 

670— What harm does a too light or too heavy gate tension 

do? . 603 


671— What is the best method of removing emulsion deposit? 605 

672— What is probable effect of worn aperture plate?.605 

673— How should sprocket idlers be adjusted, and what is 

likely to happen if they be wrongly adjusted?. 606 

674— Why is upper and lower loop necessary?. 610 

675— Tell us exactly what it is the revolving shutter does and 

how it does it. 612 

676— Why has revolving shutter more than one blade?.613 

677— What is “flicker”? Explain your answer fully. 613 

678— Exactly what does the “master blade” of shutter do?... 614 

679— What effect has speed of intermittent motion on width 

of master blade? Explain fully. 615 

680— Explain what a “60-degree” movement is, what a “60- 

degree” shutter blade is and what a “4 to 1” move¬ 
ment is ..615 and 616 

































MANAGERS AND PROJECTIONISTS 933 

681— What effect has diameter of light beam on master blade 

width? . 617 

682— What is the “aerial image” and how would you find it? 618 

683— Why should shutter usually be set at aerial image?.... 619 

684— Does it do any good to merely move revolving shutter 

to narrowest point of light beam, or what else must be 
done to get benefit ?. 620 

685— Describe best method of trimming shutter blade. 620 

686 — Is shutter sent by projector manufacturer likely to be 

suitable for use in your theatre without change?. 621 

687— Explain why it is that projector manufacturers cannot 
equip all projectors with revolving shutter having 
correct master blade width? 

688 — Explain why a 3-wing shutter is unsuitable for use with 

60-cycle A. C. 622 

689— How would you make a test to determine whether or 

not you should use a 2-wing or a 3-wing shutter?_623 

690— How would you “set the shutter”?. 623 

691— Explain action of one-and-a-half-to-one shutter. 623 

692— Explain why it is important to have as light a take-up 
tensioo as possible when using old style friction take-up 625 

693— What should be used to lubricate arc lamp?. 627 

Projector—The Lamphouse 

694— Name reasons why lamp house ventilation is important 362 

695— What is it clogs lamp house vent screens?. 363 

696— Name one reason why many lamp houses have poor ven¬ 
tilation . 362-363 

697— What is the best method of lamp house ventilation?.. 363 

698— Should lamp leads be changed frequently? Explain. . 327 

699— Is it desirable to project an image of the crater, and 

how may it be done?. 364 

700— Explain how you would arrange to automatically light 

interior of lamp house when door is opened. 365 

701— Name the requirements for a good condenser holder. . 367 

702— Is it necessary that lens and metal of holder have even 

contact? Explain fully. 367 

703— What advantage is there in locating condenser inside of 

lamp house? . 368 

704— Is there any advantage in an inside dowser?.. 368 

705— How often would you clean the interior of lamp house? 368 


Projector—The Arc Lamp 

706— What various adjustments must good lamps have?.... 370 

707— Where must lamp insulation be and of what material?.. 370 

708— What causes carbon dust grounds?. 370 

709— Tell us what care you would give lamp carbon jaws.. 371 

710— What care would you give lamp in matter of lubrication, 

and what lubricant would you use?.371 




















934 HANDBOOK OF PROJECTION FOR 

711— Will lamp leads cause loss through high resistance un¬ 
less given attention?. 372 

The Light Source (Arc) 

712— From whence does all available light come?. 390 

713— Under what condition will crater form on both carbon 

tips? . 390 

714 — When using A. C. at arc should light from both craters 

be used ? . 390 

715— Is there a difference in A. C. and D. C. light?.391 

716 — What is cause of light in electric arc crater?.391 

717— Why does crater form on positive only?. 391 

718— What amount of resistance does each element of pro¬ 
jection arc offer?.. 391 

719— What is relative temperature of electric crater and 
sun ? . 392 

720— What is approximate c. p. of crater per mm.?. 392 

721— Explain why high amperage is wasteful.394 to 399 

722— What is economic limit of amperage?...394 to 399 

723— What is absolute limit of amperage from which light 

can be gotten through projector lens system?. 398 

724 — Describe experiment proving effect of increased am¬ 
perage in light loss.394 to 399 

725— Is there a definite relation between arc voltage and cur¬ 
rent strength? . 400 

726— What is of prime importance in matter of light a 
crater will deliver to the collector lens?... 402 

727— What is relative brilliancy of A. C. arc, D. C. arc, and 

an arc supplied by mercury arc rectifier?. 401 

728— How would you lay out correct crater angle on wall or 

floor so that crater image could be projected to it. 409 


Carbons 


729— Describe, roughly, how carbons are made. 374 

730— Explain what the core is for and how it accomplishes 

its purpose .375 

731— Name the objection to cored negative. 377 

732— Name objections to solid negative. 377 

733— Explain what happens if you use either a too small or 

a too large carbon. 377 

734— What, approximately, is intrinsic brilliancy of crater 

per square millimeter of area?. 378 

735— Explain fully, and in detail, exactly what happens as 
regards crater area and candlepower when amperage 

is increased. .379 to 384 

736— At what point must a carbon be worked in order to se¬ 
cure maximum efficiency?. 38'4 

737— What is the practical effect of overloading carbons?.. 384 




























MANAGERS AND PROJECTIONISTS 935 


738— What is the practical effect of underloading carbons? 

. 379 to 384 

739— How would you determine size of carbon to use?_386 

740— What inspection should projectionist give carbons?_387 

741— What care should projectionist give to carbons?.388 

742— Are special carbons necessary with A. C. at arc?. 389 

743— Explain necessity for having carbons set straight with 

each other throughout their length. 403 

Reels 

744— Name objections to old style, small-hub reels. 281 

745— What are objections to flimsy, weak reel sides?. 281 

746— Is it advisable to have reels for use in projection room 

only, and to not use exchange reels?.281-282-322 

747— What should be limit of footage on reels?. 282 

748— How would you calculate the footage on a reel, the 

footage in a film roll, or the footage a reel holds?.... 283 

749— Name the objections to over-loading reels. 282 


Motor Generators 

750— Give various reasons why current rectification is ad¬ 
visable from projection standpoint.390 and 442 

751— What devices are available for current rectification?. . 442 

752— What are the points for and against mercury arc recti¬ 
fiers and motor generators.443 

753— What may happen to efficiency of motor generator set if 

in charge of careless or incompetent man?. 444 

754— Give your ideas as to proper location of M. G. set.... 444 

755— Name various things to be done, and points to be looked 

after in installing M. G. set.445 to 448 

756— Describe the ring oiling system.Figure 148, page 448 

757 — What kind of oil should be used on M. G. set?.448 

758— why should great care be used in selection of grease for 

ball bearings? . 449 

759 — For what reason should a heavy oil be rejected for use 

in cold weather ?... 450 

760_Is it essential that all bolts and connections be inspected 

and tightened periodically?. 450 

76l_What importance attaches to location of voltmeter and 

ammeter?. 450 

762— Name a few of the many important points in care of 

commutator .451 to 460 

763— What would you do if bearings run hot?. 460 

764— How would you test to ascertain whether or not your 

motor or generator is heating dangerously. 460 


765- 


Mercury Arc Rectifiers 

-Explain the principle of operation of rectifiers. 


515 


























936 HANDBOOK OF PROJECTION FOR 

766— With what is the “tube” or “bulb” filled when rectifier 

is in operation?. 515 

767— By what is the tube started into operation?. 515 

768— Is a vacuum in the tube necessary? 

See “Tube Tilts,” trouble chart, page 533 

769— Name the essential parts of a rectifier.. 516 

770— What office does auto transformer of rectifier fill?-516 

771 — What prevents current flowing back from vapor to 

graphite terminal?. 515 

772— Why is it essential that the rectifier be installed in a 

well ventilated place?. 518 

773 — How would you prevent light from tube showing if 

rectifier is in projection room?.517 and 518 

774— Are voltmeter and ammeter essential where rectifier is 

used ? . 520 

775— Are rectifiers so arranged that they may be connected to 

either 110 or 220-volt supply?....522 and 539 

776— What would you do if the tube went dead and you had 

no other tube?.522 and 539 

777— What are the main and regulating reactance, and what 

are they for?.522 and 537 

778— May two arcs be operated from one rectifier at the 

same time? . 522 

779— Can you vary amperage at will, within capacity of tube, 

when using rectifier?.522 and 538 

The Transformer 

780— Can a transformer be used on direct current?. 544 

781— What is the purpose of a transformer?. 544 

782— Of what four main elements do transformers consist? 544 

783— Draw diagram showing relation of coils to each other 

and to the core.544 and 549 

784— Upon what is the action of a transformer based?. 544 

785— Explain how the basic principle referred to in question 

No. 784 is applied. 54S 

786— What is meant by an “induced” current?. 545 

787— What happens when the primary current is increased 

or decreased? .545 and 546 

788'—Name the two types of transformer used for projection 

work and describe them. 546 

789— What is the efficiency of a well designed transformer, 

and what do the losses consist of?. 547 

790— Of what is a transformer core made, and how it is put 

together ? . 547 

791— What is meant by “ratio of transformation”?. 547 

792— What is the difference in a “step-up” and “step-down” 

transformer? . 548 

793— The wires of secondary coil of inductor, economizer or 

























MANAGERS AND PROJECTIONISTS 


937 


compensarc are larger than wires of primary coil. Why 
is this so? . 

794— Are the coils and core electrically insulated from each 

other? .. 

795— Upon what does the ratio of transformation depend?.. 

796— Name three low voltage projection transformers. 

797— Is it possible to vary the amperage when using a pro¬ 
jection transformer? . 

798— In what way is variation of amperage accomplished?.. 

799— How hot may your inductor, economizer or other pro¬ 
jection transformer get without danger to it?. 

800— What size wires would you use when installing a pro¬ 
jection transformer? . 

801— What is a “choke coil” and how does it act?. 

802— Does a choke coil give good results when used for pro¬ 
jection work? . 

803— Could you connect two projection transformers in 

multiple ? .. 

804— Draw diagram showing how to connect projection trans¬ 
former to line and lamp.Figure 205, page 

805— Where should projection transformer be located?. 

Arc Controllers 

806— What is the difference in an “automatic” and a mechani¬ 
cal arc feed controller?.559 and 

807— Upon what does an automatic control depend for its 

action? .559 and 

808— In what way does a mechanical arc feed controller 

operate ? ... 

809— What reasons are there why arc controllers should be 

used? .559 and 

High Intensity Arc 

810— Name three advantages the high intensity has over the 

ordinary arc for projection purposes. 

811— What is relative brilliancy of high intensity and ordi¬ 
nary arc crater?. 

The Spotlight 

812— What kind of lens is used in spotlight?. 

813— What skill is necessary to successfully handle a spot and 

get good results?.794 and 

814— How is spot made larger or smaller?. 

815— What will be the result if wrong carbons are used?... 

816— What lens would you require to get a five-foot spot at 

150 feet? . 

The Stereopticon 

817— Why does a crack in condenser show in the stereo 


548 

548 

548 

549 

549 

550 

550 

550 

550 

551 

551 

555 

552 

560 

560 

560 

561 

773 

869 

794 

795 

794 

798 

799 























938 


HANDBOOK OF PROJECTION FOR 


picture and not in a motion picture ?... 

818 — What objections are there to projecting slides with com¬ 
bination projector, and how may they be overcome?.. 

819— What are advantages of dissolver over single stere- 

opticon ? . 

820— Describe method by means of which one picture is dis¬ 
solved into another... 

821— How would you make a dissolving shutter ?. 

822— Why is it necessary to have a longer focal length stereo 

lens than a M. P. lens for same size picture at same 
distance ? . 

823— What should be the proportions of slide mats?.. 

824— Is it possible to get a semi-dissolving effect with a single 

stereoprticon ? . 


801 

802 

804 

805 

806 

808 

808 

808 


825—Give one or more methods of making slides to convey 

messages to the audience.811 to 814 


Madza Lamp Projection 

826— Can Mazda equal electric arc in brilliancy?. 815 

827— Why is spherical mirror placed back of Mazda lamp?.. 817 

828— The spherical mirror reflects and focuses an image. 

Exactly where must this image be?.817 and 819 

829— Describe the Mazda projection lamp, in detail. 817 

830— What is meant by “short circuiting in filament coils,” 

and what is effect of it?. 819 

831— Describe action of filament under expansion and con¬ 
traction, Figure 321 and text. 820 

832— What causes blackening of bulb, and what is its effect? 821 

833— What is comparative quality of light from Mazda and 

from electric arc?. 822 

834— What is relative light collecting power of large and 

small diameter projection lenses when using prismatic 
condenser ? . 825 

835— Is location of center of lamp filament exactly on optical 

axis of great importance?. 836 

836— How would you locate center of filament on optical 

axis? . 837 

837— Name the advantages of Mazda lamp projection. 842 

838— Can man of small ability handle Mazda lamp projection 

successfully?. 848' 

839— Name the advantages claimed for piano convex system 

of condensing ..-. 854 

840— Describe process of placing lamp in holder and in lamp 

house when using piano convex.861 to 864 

841— Are focal distances, Figure 362, page 865, fixed and im¬ 
portant? . 866 

842— Describe correct method of locating lamp filament 

image and lamp filament.865 to 868 

























MANAGERS AND PROJECTIONISTS 


939 


Ready — 


EASTMAN 
FILM CEMENT 


Cut where you will, splice with 
Eastman Film Cement and for 
all practical purposes the reel’s 
original resistance to strain both 
in projection and re-wind is 
restored. The splice is secure 
against break or buckle. 

Eastman-made and Eastman-tested as the 

presence of this seal on the container testifies: 



Eastman Film Cement is the only cement 
that may be used successfully with either 
Regular or Safety film. It may be obtained 
in i oz. and 16 oz. bottles, and gallon 
containers. 

EASTMAN KODAK COMPANY 

Motion Picture Film Department ROCHESTER, N. Y. 



940 


HANDBOOK OF PROJECTION FOR 


Complete Equipment 
for the Projection Room 

The General Electric Company 
manufactures the following material 
for superior projection of motion pic¬ 
tures: 

G-E Mazda Lamp Projector 

G-E High Intensity Arc Lamp 

G-E Alternating Current Com- 
pensarc 

G-E Motor Generator Compen- 
sarcs (A. C. to D. C. & D. C. to D. C.) 


G-E apparatus is safe, easy to oper¬ 
ate, efficient, economical and reliable. 
G-E offices or distributors everywhere 
are able to give prompt deliveries and 
satisfactory service. Literature on all 
types of apparatus on request. 


GeneralfpElectrlc 

General Office CO!Mpa.!iy Sche £ e £ ad y. 


MANAGERS AND PROJECTIONISTS 941 



Fool-Proof Splicing Machine 

Good cement will weld films, but if 
the alignment of the film ends is 
poor the best weld must fail, 
due to the interference with 

the sprocket teeth. 


The pilot system of our 
splicing machine lo¬ 
cates the film ends ac¬ 
curately and produces 
only good lasting 
splices. 


All users agree that it is 
the best they ever saw or 
had. 


Sold by all dealers. 


GENERAL MACHINE COMPANY 

Manufacturers Owning All Rights 
359-63 East 155th Street New York City, U. S. A. 


) YOU 

KNOW 

Fi 

II 

LI 

M 



AST 


TRADE MARK 

That is the name of a NEW Projecting Reel that 
will give you these Guaranteed Advantages— 

1. Speed and Ease of attaching 
film to reel—a patented spring 
allows just two fingers of one 
hand to firmly fasten film end 
—at once—quickly—no blind 
trying. 

2. Speed in patching breaks—a 
superior steel and a design that * 
came from studying your prob¬ 
lems. 

3. Durability—in the greatest de¬ 
gree, because it is a scientific¬ 
ally tested construction. 

4. True running—always. 

Why not drop a card and tell us it’s up to us 

to “‘show” you ? 

FRANK MOSSBERG CO., P. O. Box 420, Attleboro, Mass. 


















942 


HANDBOOK OF PROJECTION FOR 


RE RICHARDSON 

PROJECTION ENGINEER 


$25 $25 $25 $25 $25 $25 $25 


The author of this book will ex¬ 
amine theatre plans and advise as to 
what, if any, changes should be made 
to secure the best possible results in 
projection. 

This will include advice as to ex¬ 
actly what the side distortion will be 
from front side seats and will include 
advice as to what type of screen sur¬ 
face will be best for the auditorium. 
The charge will be twenty-five dol¬ 
lars, which must accompany the 
plans, because I am making the 
charge very low, hence cannot be put 
to the expense of bookkeeping. 


Address R H* RICHARDSON 

No. 12 TRENO STREET 
HALCYON PARK, NEW ROCHELLE, N.Y. 































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The mark of a SERVICE 




When you purchase 
Motion Picture Equipment, 
you get apparatus properly 
designed to give reliable ser¬ 
vice at maximum efficiency— 
This is SERVICE that counts. 

Save money by consulting us 
on the following lines before 
deciding on your installation 
of motion picture equipment: 

zi-r-z Proctor Automatic 

Projectors 

Hallberg Motor Generators 
Arc Controllers, Electric 
Speed 

Indicators and Recorders 
A. C. Economizers, 4 in 1 
Mazda 

Regulators, Hallberg Portable 
Projectors and Feather¬ 
weight Electric Plants 

Magic Carbon 

Holders 

Also screens, carbons, reels, carry¬ 
ing cases, tickets and other sup¬ 
plies. 

We solicit your order for high class equipment. 


UNITED THEATRE 
EQUIPMENT CORP. 

25 WEST 45th STREET NEW YORK 

H. T. EDWARDS J. H. HALLBERG 

President Vice-President 

Branch Stores in All Principal Cities 
Everything for the Motion Picture Theatre Except the Film. 





is particularly recommended 

TO THE READERS OF THIS 
BOOK 


for its 

SIMPLICITY 

EASE OF OPERATION 
WEARING QUALITIES 
WORKMANSHIP and 
ALL AROUND GENERAL 

SUPERIORITY 

That’s why the majority of 
representative American cities 
are more than 75% simplexized 


ThePrec™ M achine (o .Tnc. 

317 East 34th:St- NewYork 


































































